Integrated illumination of optical analytical devices

ABSTRACT

Optical analytical devices and their methods of use are provided. The devices are useful in the analysis of highly multiplexed optical reactions in large numbers at high densities, including biochemical reactions, such as nucleic acid sequencing reactions. The devices include integrated illumination elements and optical waveguides for illumination of the optical reactions. The devices further provide for the efficient coupling of optical excitation energy from the waveguides to the optical reactions. Optical signals emitted from the reactions can thus be measured with high sensitivity and discrimination using features such as spectra, amplitude, and time resolution, or combinations thereof. The devices of the invention are well suited for miniaturization and high throughput.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/187,198, filed on Feb. 21, 2014, and claims the benefit under 35U.S.C. § 119(e) of U.S. Provisional Application No. 61/768,053, filed onFeb. 22, 2013, the disclosures of which are incorporated herein byreference in their entireties.

BACKGROUND OF THE INVENTION

In analytical systems, the ability to increase the number of analysesbeing carried out at any given time by a given system has been a keycomponent to increasing the utility and extending the lifespan of suchsystems. In particular, by increasing the multiplex factor of analyseswith a given system, one can increase the overall throughput of thesystem, thereby increasing its usefulness while decreasing the costsassociated with that use.

In optical analyses, increasing multiplex often poses increaseddifficulties, as it may require more complex optical systems, increasedillumination or detection capabilities, and new reaction containmentstrategies. In some cases, systems seek to increase multiplex by manyfold, and even orders of magnitude, which further implicate theseconsiderations. Likewise, in certain cases, the analytical environmentfor which the systems are to be used is so highly sensitive thatvariations among different analyses in a given system may not betolerable. These goals are often at odds with a brute force approach ofsimply making systems bigger and of higher power, as such steps oftengive rise to even greater consequences, e.g., in inter reactioncross-talk, decreased signal to noise ratios resulting from either orboth of lower signal and higher noise, and the like. It would thereforebe desirable to provide analytical systems that have substantiallyincreased multiplex for their desired analysis, and particularly for usein highly sensitive reaction analyses, and in many cases, to do so whileminimizing negative impacts of such increased multiplex.

Conventional optical systems employ complex optical trains that direct,focus, filter, split, separate, and detect light to and/or from thesample materials. Such systems typically employ an assortment ofdifferent optical elements to direct, modify, and otherwise manipulatelight directed to and/or received from a reaction site. Such systems aretypically complex and costly and tend to have significant spacerequirements. For example, typical systems employ mirrors and prisms indirecting light from its source to a desired destination. Additionally,such systems may include light-splitting optics such as beam-splittingprisms to generate two or more beams from a single original beam.

There is a continuing need to increase the performance of analyticalsystems and reduce the cost associated with manufacturing and using thesystem. In particular, there is a continuing need to increase thethroughput of analytical systems. There is a continuing need to reducethe size and complexity of analytical system. There is a continuing needfor analytical systems that have flexible configurations and are easilyscalable.

SUMMARY OF THE INVENTION

The present disclosure addresses these and other needs by providing ananalytical device comprising:

a substrate;

an integrated illumination element;

a plurality of illumination volumes; and

a plurality of detector elements.

In one aspect, the disclosure provides an analytical device wherein theintegrated illumination element is disposed in the substrate, theintegrated illumination element comprises an optical resonator within awaveguide, the optical resonator comprises a laser medium and a firstand a second mirror disposed within the waveguide, and the plurality ofillumination volumes are contained in a plurality of nanowells disposedon a surface of the substrate, wherein at least a first nanowell isoptically coupled to the waveguide and to one of the detector elements.

In some embodiments of this aspect of the invention, the first nanowellis optically coupled to the waveguide by evanescent illuminationemanating from the waveguide.

In some embodiments, the first mirror and the second mirror are 100%reflection mirrors, and the first nanowell is optically coupled to thewaveguide at a region directly adjacent to the optical resonator.

In some embodiments, no more than one nanowell or row of nanowells iscoupled to the waveguide.

In some embodiments, the first mirror is a high reflector mirror and thesecond mirror is a partial reflector mirror.

In some embodiments, the optical resonator amplifies optical energy inthe waveguide.

In some embodiments, the first nanowell is optically coupled to thewaveguide at a region remote from the optical resonator.

In some embodiments, the analytical device further comprises a secondnanowell optically coupled to the waveguide by evanescent illuminationemanating from the waveguide, wherein the first nanowell is opticallycoupled to the waveguide at a region directly adjacent to the opticalresonator and the second nanowell is optically coupled to the waveguideat a region remote from the optical resonator.

In some embodiments, the integrated illumination element of the devicecomprises a plurality of optical resonators within a waveguide, eachoptical resonator comprising a laser medium and a first and a secondmirror disposed within the waveguide; and wherein the first nanowell isoptically coupled to the integrated illumination element.

In some embodiments, at least one of the optical resonators amplifiesoptical energy in the waveguide, and in some embodiments, the firstnanowell is optically coupled to the waveguide at a region remote fromthe optical resonators.

In some embodiments of the device, at least one optical resonator isoptically pumped, and in some embodiments, at least one opticalresonator is electrically pumped.

In another aspect, the disclosure provides an analytical device whereinthe integrated illumination element is disposed on the surface of thesubstrate, the plurality of detector elements are disposed below thesurface of the substrate, the integrated illumination element is partlysurrounded by an opaque layer, and the plurality of illumination volumesare contained in a plurality of nanowells disposed on a surface of thesubstrate, wherein at least a first nanowell is optically coupled to theintegrated illumination element and to one of the detector elements.

In certain embodiments according to this aspect of the device, the firstnanowell comprises a bottom surface and a first side surface. The firstnanowell in these embodiments may be optically coupled to the integratedillumination element through the first side surface of the firstnanowell, and the opaque layer may partly cover the first side surfaceof the first nanowell. In other embodiments, the opaque layer does notcover the first side surface of the first nanowell.

In some embodiments, the first nanowell is optically coupled to theintegrated illumination element through the bottom surface of the firstnanowell, and the opaque layer may completely cover the first sidesurface of the first nanowell.

In some embodiments of the device, the first nanowell is opticallycoupled to the integrated illumination element through a transferwaveguide disposed in the substrate, and the transfer waveguide may, insome embodiments, illuminate no more than one of the nanowells, whereasin other embodiments, the transfer waveguide may illuminate more thanone of the nanowells.

In some embodiments, the first nanowell of the analytical device may beoptically coupled to the detector element through the bottom surface ofthe first nanowell, and the first nanowell may further comprise a secondside surface, wherein the second side surface comprises a micromirror.In some of these embodiments, the micromirror may increase the opticalcoupling of an illumination volume contained in the first nanowell tothe integrated illumination element.

In some embodiments, the second side surface may have a concave shape ormay be angled toward the bottom surface of the first nanowell.

In some embodiments of the device, the opaque layer partly surroundingthe integrated illumination element comprises a micromirror, which may,in some embodiments, increase the optical coupling of an illuminationvolume contained in the first nanowell to the integrated illuminationelement.

In some embodiments, the opaque layer partly surrounding the integratedillumination element is cylindrical.

In some embodiments, the analytical device further comprises a filterlayer disposed between the surface of the substrate and the plurality ofdetector elements, and the filter layer may decrease the transmission ofoptical energy from the integrated illumination element to the pluralityof detector elements.

In some embodiments, at least one detector element of the plurality ofdetector elements in the device further comprises a microlens or a lightredirection cone.

In some embodiments of the analytical device, the integratedillumination element comprises a waveguide, a discrete light source, ora light-emitting diode or a semiconductor laser diode.

In yet another aspect, the disclosure provides an analytical devicewherein the integrated illumination element comprises a plurality ofdiscrete light sources disposed on the surface of the substrate.

According to some embodiments, the device further comprises an opaquelayer disposed on the surface of the substrate.

In some embodiments, the plurality of detector elements are disposedbelow the surface of the substrate, whereas in other embodiments, theplurality of detector elements are disposed above the opaque layer. Insome embodiments, the device further comprises a cover slip disposedbetween the opaque layer and the plurality of detector elements.

In some embodiments, the plurality of illumination volumes are containedin a plurality of nanowells disposed on a surface of the substrate,wherein at least a first nanowell is optically coupled to one of thediscrete light sources and to one of the detector elements. In some ofthese devices, the device further comprises an opaque layer disposed onthe surface of the substrate, wherein the plurality of nanowells aredisposed in the opaque layer, and wherein the first nanowell comprises abottom surface and a first side surface. In some embodiments, the firstnanowell is optically coupled to a first discrete light source throughthe bottom surface of the first nanowell, and in some embodiments, thefirst nanowell is optically coupled to the first discrete light sourcethrough the first side surface of the first nanowell.

In some embodiments, the device further comprises a conductor elementand an insulator element associated with the first discrete lightsource, wherein the insulator element is disposed between the conductorelement and the opaque layer.

According to some embodiments, the plurality of discrete light sourcesin the analytical device is a plurality of light-emitting diodes or aplurality of semiconductor laser diodes. In some embodiments, theplurality of semiconductor laser diodes is a plurality of verticalcavity surface-emitting lasers. In some embodiments, the plurality ofvertical cavity surface-emitting lasers are tuned to emit an evanescentillumination from an upper reflector.

According to some embodiments, the analytical device further comprisesan analyte disposed within at least one illumination volume. In someembodiments, the analyte comprises a biological sample, and, in someembodiments, the biological sample comprises a nucleic acid and/or apolymerase enzyme.

In some embodiments, the analytical device comprises at least 1,000, atleast 10,000, at least 100,000, at least 1,000,000, or at least10,000,000 illumination volumes.

In some embodiments of the device, at least one detector element of theplurality of detector elements further comprises a spectral diversionelement, and in some embodiments, at least one detector element of theplurality of detector elements further comprises a light redirectioncone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B schematically illustrates an exemplary nucleic acidsequencing process that can be carried out using aspects of theinvention.

FIG. 2 provides a schematic block diagram of an integrated analyticaldevice.

FIG. 3A provides a schematic of excitation spectra for two signal eventsand an indicated narrow band excitation illumination, while FIG. 3Bschematically illustrates the resulting detected signal based upon thenarrow band illumination of the two signal events.

FIG. 4 schematically illustrates the signal profiles for each of fourfluorescent labeling groups, overlain with each of two different filterprofiles.

FIG. 5 schematically illustrates an integrated analytical device fordetecting signals from a 4-color sequencing reaction.

FIG. 6 schematically illustrates signal traces for a two-color,two-amplitude sequence-by-synthesis reaction.

FIG. 7A illustrates an analytical device containing a waveguide core,cladding, metallic/opaque layer, and a material of high dielectric ormetal in the vicinity of the nanometer-scale aperture, as viewed in thex-z plane. FIG. 7B illustrates an alternative device structure, having ageometric pattern of high dielectric material or metal surrounding theaperture. FIG. 7C illustrates another alternative device structure,having a decreased cladding thickness in the regions of the waveguideadjacent to the aperture and/or an increased cladding thickness in theregions not adjacent to the aperture. The device of FIG. 7C additionallyincludes a high dielectric material or metal in the vicinity of theaperture.

FIGS. 8A-8B illustrate an analytical device where the thickness of thecladding is decreased in the regions of waveguide adjacent to theaperture, and the device additionally contains a stray light terminationmaterial. FIG. 8A shows a top view in the x-y plane with the opaque,metallic layer omitted from the view. FIG. 8B shows a cross-sectionalview in the y-z plane.

FIGS. 9A-9C provide a schematic of the design used in simulations ofcoupling efficiencies. FIG. 9A shows a top view of the simulated devicein the x-y plane with the opaque, metallic layer omitted from the view.FIG. 9B shows a side view of the simulated device in the x-z plane. FIG.9C shows a cross-sectional view of the simulated device in the y-zplane.

FIGS. 10A-10B illustrate an example of the dimensional modulation of thewaveguides.

FIGS. 11A-11B illustrate an example of a device with a “slotted”waveguide. FIG. 11A: cross-sectional view; FIG. 11B: top-down view.

FIGS. 12A-12B show the configuration and optical modes of a waveguidecontaining a non-linear optical material in the core (FIG. 12A) and inpart of the cladding (FIG. 12B).

FIGS. 13A-13B illustrate configurations of waveguides containingnon-linear optical materials.

FIGS. 14A-14B schematically illustrate a waveguide containing awavelength conversion element just after the coupler (FIG. 14A) andanother exemplary waveguide with independently addressable SHG elements(FIG. 14B).

FIGS. 15A-15G illustrate examples of devices containing opticalresonators integrated into waveguides disposed within the substrate. Ineach case, the waveguide is integrated into the device in a layer belowthe layer containing the nanowells. Double-headed arrows within thewaveguide represent the confinement of optical energy along the cavitydirection. The optical energy is confined inside the cavity as astanding wave. Single-headed arrows within the waveguide representtransmission of optical energy along the waveguide. The large arrow inFIG. 15F represents an optical pump having equal or shorter wavelength.The device shown attached to the left end of the waveguide in FIG. 15Grepresents an electrical pump.

FIGS. 16A-16G illustrate exemplary devices with integrated illuminationabove the surface of the substrate. The illumination element may beeither a waveguide source or a discrete light source, as furtherdescribed herein. In each case, the illumination element is disposed inthe same layer of the device as the nanowells. The opaque layer, asillustrated by thick lines in the drawings, may be a metallic layer.

FIGS. 17A-17C illustrate variants of the devices of FIGS. 16A-16G withimproved excitation coupling.

FIG. 18 illustrates a variant of the devices of FIGS. 16A-16G withimproved detection.

FIG. 19 illustrates a variant of the devices of FIGS. 16A-16G withadditional spacing between the excitation source and the opaque layer.

FIG. 20 illustrates a variant of the devices of FIGS. 16A-16G withadditional detector features.

FIGS. 21A-21B show exemplary analytical devices with integrated LEDelements, where detection is either below the device, through atransparent substrate (FIG. 21A), or above the device, where thesubstrate is opaque (FIG. 21B).

FIG. 22 shows an exemplary analytical device with an integrated LEDelement, where excitation is from the side of a nanowell and detectionis above or below the nanowell.

FIG. 23A shows an exemplary analytical device with an integrated,transparent LED element, where excitation is from below the nanowell anddetection is above or below the nanowell; FIG. 23B shows in more detailthe conductors connected to the LED and their insulation.

FIG. 24 illustrates an exemplary analytical device having an integratedLED element but no metallic layer or nanowell.

FIG. 25 illustrates various patterns of LEDs or other discrete lightsources.

FIG. 26 shows the source of background diffusion noise in a device thatlacks a nanowell for sample containment.

FIG. 27 shows the structure of an exemplary cavity resonator device withhigh reflector mirrors to minimize light emission.

FIG. 28 illustrates the structure of a VCSEL (top) for use in ananalytical device containing an opaque, metallic layer and a nanowell(bottom). The top mirror of the VCSEL is a partial reflector to allowfor some light transmission.

FIG. 29 illustrates another embodiment of a cavity resonator device(left) for use in an analytical device that may optionally include nonanowell (right). The device is tuned to minimize light emission. Thegraph on the left of the drawing illustrates an evanescent fieldemanating from the surface of the device. Excitation coupling of thesample results from the evanescent field.

FIG. 30 illustrates a cross-sectional view of a portion of an exemplarydevice in which the waveguides and the nanowells are disposed in thesame layer of the device. The waveguides thus provide illumination fromthe side of the nanowells.

DETAILED DESCRIPTION OF THE INVENTION

Integrated Optical Detection Devices

Multiplexed optical analytical systems are used in a wide variety ofdifferent applications. Such applications can include the analysis ofsingle molecules, and can involve observing, for example, singlebiomolecules in real time as they carry out reactions. For ease ofdiscussion, such multiplexed systems are discussed herein in terms of apreferred application: the analysis of nucleic acid sequenceinformation, and particularly, single molecule nucleic acid sequenceanalysis. Although described in terms of a particular application, itshould be appreciated that the applications for the devices and systemsdescribed herein are of broader application.

In the context of single molecule nucleic acid sequencing analyses, asingle immobilized nucleic acid synthesis complex, comprising apolymerase enzyme, a template nucleic acid, whose sequence is beingelucidated, and a primer sequence that is complementary to a portion ofthe template sequence, is observed in order to identify individualnucleotides as they are incorporated into the extended primer sequence.Incorporation is typically monitored by observing an opticallydetectable label on the nucleotide, prior to, during, or following itsincorporation. In some cases, such single molecule analyses employ a“one base at a time approach”, whereby a single type of labelednucleotide is introduced to and contacted with the complex at a time.Upon reaction, unincorporated nucleotides are washed away from thecomplex, and the labeled incorporated nucleotides are detected as a partof the immobilized complex.

In some instances, only a single type of nucleotide is added to detectincorporation. These methods then require a cycling through of thevarious different types of nucleotides (e.g., A, T, G and C) to be ableto determine the sequence of the template. Because only a single type ofnucleotide is contacted with the complex at any given time, anyincorporation event is, by definition, an incorporation of the contactednucleotide. These methods, while somewhat effective, generally sufferfrom difficulties when the template sequence includes multiple repeatednucleotides, as multiple bases may be incorporated that areindistinguishable from a single incorporation event. In some cases,proposed solutions to this issue include adjusting the concentrations ofnucleotides present to ensure that single incorporation events arekinetically favored.

In other cases, multiple types of nucleotides are added simultaneously,but the nucleotides are distinguishable by the presence on each type ofnucleotide a different optical label. Accordingly, such methods can usea single step to identify a given base in the sequence. In particular,all four nucleotides, each bearing a distinguishable label, are added tothe immobilized complex. The complex is then interrogated to identifywhich type of base was incorporated, and as such, the next base in thetemplate sequence.

In some cases, these methods only monitor the addition of one base at atime, and as such, they (and in some cases, the single nucleotidecontact methods) require additional controls to avoid multiple basesbeing added in any given step, and thus being missed by the detectionsystem. Typically, such methods employ terminator groups on thenucleotide that prevent further extension of the primer once onenucleotide has been incorporated. These terminator groups are typicallyremovable, allowing the controlled re-extension after a detectedincorporation event. Likewise, in order to avoid confounding labels frompreviously incorporated nucleotides, the labeling groups on thesenucleotides are typically configured to be removable or otherwiseinactivatable.

In another example, single molecule primer extension reactions aremonitored in real time, to identify the continued incorporation ofnucleotides in the extension product to elucidate the underlyingtemplate sequence. In such single molecule real time (or SMRT™)sequencing, the process of incorporation of nucleotides in apolymerase-mediated template-dependent primer extension reaction ismonitored as it occurs. In preferred aspects, the template/polymeraseprimer complex is provided, typically immobilized, within anoptically-confined region, such as a zero mode waveguide (ZMW), orproximal to the surface of a transparent substrate, optical waveguide,or the like (see e.g., U.S. Pat. Nos. 6,917,726, 7,170,050, and7,935,310, the full disclosures of which are hereby incorporated byreference herein in their entirety for all purposes). Theoptically-confined region is illuminated with an appropriate excitationradiation for the fluorescently-labeled nucleotides that are to be used.Because the complex is within an optically confined region, or verysmall illumination volume, only the reaction volume immediatelysurrounding the complex is subjected to the excitation radiation.Accordingly, those fluorescently labeled nucleotides that areinteracting with the complex, e.g., during an incorporation event, arepresent within the illumination volume for a sufficient time to identifythem as having been incorporated.

A schematic illustration of this sequencing process is shown in FIGS.1A-1B. As shown in FIG. 1A, an immobilized complex 102 of a polymeraseenzyme, a template nucleic acid and a primer sequence are providedwithin an observation volume (as shown by dashed line 104) of an opticalconfinement, of e.g., a zero mode waveguide 106. As an appropriatenucleotide analog, e.g., nucleotide 108, is incorporated into thenascent nucleic acid strand, it is illuminated for an extended period oftime corresponding to the retention time of the labeled nucleotideanalog within the observation volume during incorporation. Theincorporation reaction thus produces a signal associated with thatretention, e.g., signal pulse 112 as shown by the A trace in FIG. 1B.Once incorporated, the label that was attached to the polyphosphatecomponent of the labeled nucleotide analog, is released. When the nextappropriate nucleotide analog, e.g., nucleotide 110, is contacted withthe complex, it too is incorporated, giving rise to a correspondingsignal 114 in the T trace of FIG. 1B. By monitoring the incorporation ofbases into the nascent strand, as dictated by the underlyingcomplementarity of the template sequence, long stretches of sequenceinformation of the template can be obtained.

The above sequencing reaction may be incorporated into a device,typically an integrated analytical device, that provides for thesimultaneous observation of multiple sequencing reactions, ideally inreal time. While the components of each device, and the configuration ofthe devices in the system, may vary, each integrated analytical devicetypically comprises, at least in part, the general structure shown as ablock diagram in FIG. 2. As shown, an integrated analytical device 200typically includes a reaction cell 202, in which the reactants aredisposed and from which the optical signals emanate. The analysis systemfurther includes a detector element 220, which is disposed in opticalcommunication with the reaction cell 202. Optical communication betweenthe reaction cell 202 and the detector element 220 may be provided by anoptical train 204 comprised of one or more optical elements generallydesignated 206, 208, 210 and 212 for efficiently directing the signalfrom the reaction cell 202 to the detector 220. These optical elementsmay generally comprise any number of elements, such as lenses, filters,gratings, mirrors, prisms, refractive material, or the like, or variouscombinations of these, depending upon the specifics of the application.By integrating these elements into a single device architecture, theefficiency of the optical coupling between the reaction cell and thedetector is improved. Examples of integrated analytical systems,including various approaches for illuminating the reaction cell anddetecting optical signals emitted from the reaction cell, are describedin U.S. Patent Application Publication Nos. 2012/0014837, 2012/0019828,and 2012/0021525, which are each incorporated by reference herein intheir entireties for all purposes.

Conventional analytical systems typically measure multiple spectrallydistinct signals or signal events and must therefore utilize complexoptical systems to separate and distinctly detect those different signalevents. The optical path of an integrated device may be simplified,however, by a reduction in the amount or number of spectrallydistinguishable signals that are detected. Such a reduction is ideallyeffected, however, without reducing the number of distinct reactionevents that can be detected. For example, in an analytical system thatdistinguishes four different reactions based upon four differentdetectable signal events, where a typical system would assign adifferent signal spectrum to each different reaction, and thereby detectand distinguish each signal event, in an alternative approach, fourdifferent signal events would be represented at fewer than fourdifferent signal spectra, and would, instead, rely, at least in part, onother non-spectral distinctions between the signal events.

For example, a sequencing operation that would conventionally employfour spectrally distinguishable signals, e.g., a “four-color” sequencingsystem, in order to identify and characterize the incorporation of eachof the four different nucleotides, would, in the context of analternative configuration, employ a one-color or two-color analysis,e.g., relying upon a signals having only one or two distinct ordistinguished spectral signals. However, in such an alternativeconfiguration, this reduction in reliance on signal spectral complexitydoes not come at the expense of the ability to distinguish signals frommultiple, i.e., a larger number of different signal producing reactionevents. In particular, instead of relying solely on signal spectrum todistinguish reaction events, such an alternative configuration may relyupon one or more signal characteristics other than emission spectrum,including, for example, signal intensity, excitation spectrum, or bothto distinguish signal events from each other.

In one particular alternative configuration, the optical paths in anintegrated analytical device may thus be simplified by utilizing signalintensity as a distinguishing feature between two or more signal events.In its simplest iteration, and with reference to an exemplary sequencingprocess, two different types of nucleotides would bear fluorescentlabels that each emit fluorescence under the same excitationillumination, i.e., having the same or substantially overlappingspectral band, and thus would provide benefits of being excited using asingle excitation source and beam. The resulting signals from eachfluorescent label would have distinct signal intensities or amplitudesunder that same illumination, and would be distinguishable by theirrespective signal amplitudes. These two signals could have partially orentirely overlapping emission spectra, but separation of the signalsbased upon any difference in emission spectrum would be unnecessary.

Accordingly, for analytical systems using two or more signal events thatdiffer in signal amplitude, the integrated analytical devices of suchsystems can readily benefit through the removal of some or all of thosecomponents that would normally be used to separate spectrally distinctsignals, such as multiple excitation sources and their associatedoptical trains, as well as the color separation optics, e.g., filtersand dichroics, for the signal events, which in many cases, requires atleast partially separate optical trains and detectors for eachspectrally distinct signal. As a result, the optical paths for theseintegrated analytical devices are greatly simplified, allowing placementof detector elements in closer proximity to reaction regions, andimproving overall performance of the detection process for thesedevices.

Provision of signal-producing reactants that will produce differentsignal amplitudes under a particular excitation illumination profile maybe accomplished in a number of ways. For example, different fluorescentlabels may be used that present excitation spectral profiles thatoverlap but include different maxima. As such, excitation at a narrowwavelength will typically give rise to differing signal intensities foreach fluorescent group. This is illustrated in FIG. 3A, which shows theexcitation spectra of two different fluorescent label groups (solid anddashed lines 302 and 304, respectively). When subjected to excitationillumination at the wavelength range shown by vertical lines 306, eachfluorescent label will emit a signal at the corresponding amplitude. Theresulting signal intensities at a given excitation wavelength are thenshown in the bar chart of FIG. 3B, shown as the solid lined and dashedlined bars, respectively. The difference in intensity of these twosignal-producing labels at the given excitation wavelength can then bereadily used to distinguish the two signal events. As will beappreciated, such spectrally indistinct signals would not be easilydistinguishable when occurring simultaneously, as they would result inan additive overlapping signal, unless, as discussed below, suchspectrally indistinct signals result from spectrally distinct excitationwavelengths. As will be appreciated, this same approach may be used withmore than two label groups where the resulting emission at a givenexcitation spectrum have distinguishable intensities or amplitudes.

Similarly, two different fluorescent labeling groups may have the sameor substantially similar excitation spectra, but provide different anddistinguishable signal emission intensities due to the quantum yield orextinction coefficient of those labeling groups.

Further, although described in terms of two distinct fluorescent dyes,it will be appreciated that each different labeling group may eachinclude multiple labeling molecules. For example, each reactant mayinclude an energy transfer dye pair that yields emissions of differingintensities upon excitation with a single illumination source. Forexample, a labeling group may include a donor fluorophore that isexcited at a given excitation wavelength, and an acceptor fluorophorethat is excited at the emission wavelength of the donor, resulting inenergy transfer to the acceptor. By using different acceptors, whoseexcitation spectra overlap the emission spectrum of the donor todiffering degrees, such an approach can produce overall labeling groupsthat emit at different signal amplitudes for a given excitationwavelength and level. Likewise, adjusting the energy transfer efficiencybetween the donor and acceptor will likewise result in differing signalintensities at a given excitation illumination. Examples of theseapproaches are described in U.S. Patent Application Publication No.2010/0255488, the full disclosure of which is incorporated by referenceherein in its entirety for all purposes.

Alternatively, different signal amplitudes may be provided by differentmultiples of signal producing label groups on a given reactant, e.g.,putting a single label molecule on one reactant while putting 2, 3, 4 ormore individual label molecules on a different reactant. The resultingemitted signal will be reflective of the number of labels present on areactant and thus will be indicative of the identity of that reactant.Methods and compositions for coupling multiple labeling groups onreactants, such as nucleotide analogs, are described in, for example,U.S. patent application Ser. No. 13/218,312, filed Aug. 25, 2011, andincorporated by reference herein in its entirety for all purposes.

As described above, integrated analytical devices making use of suchapproaches see a reduction in complexity by elimination of spectraldiscrimination requirements, e.g., using signal amplitude or othernon-spectral characteristics as a basis for signal discrimination.Integrated analytical devices that combine such non-spectraldiscrimination approaches with the more common spectral discriminationapproaches may also provide advantages over more complex spectraldiscrimination systems. By shifting from a “four-color” discriminationsystem to a system that distinguishes signals based upon signalintensity and color, one can still reduce the complexity of the overalloptical system relative to a conventional four-color separation scheme.For example, in an analytical operation that detects four discretereaction events, e.g., in a nucleic acid sequencing analysis, two signalevents may be provided within a given emission/detection spectrum, i.e.,emitting signals within the same spectral window, and the other twoevents within a distinct emission/detection spectrum. Within eachspectral window, the pair of signal events produce distinguishablesignal intensities relative to each other.

For ease of discussion, this concept is described in terms of two groupsof fluorescent signal events, where members of each group differ byfluorescent intensity, and the groups differ by virtue of their emissionspectrum. As will be appreciated, the use of simplified optics systems,e.g., using two detection channels for two distinct emission spectra,does not require that the emission profiles of the two groups of signalsdo not overlap or that the emission spectra of members of each groupperfectly overlap. Instead, in many preferred aspects, more complexsignal profiles may be used where each different signal event possessesa unique emission spectrum, but in a way that each signal will present asignal profile within the two detection channels that is unique, basedupon the signal intensity in each channel.

FIG. 4 schematically illustrates the signal profiles for each of fourfluorescent labeling groups, overlain with each of two different filterprofiles. As shown, four label groups yield emission spectra 402, 404,406 and 408, respectively. While the signals from these four groupspartially overlap each other, they each have different maxima. Whensubjected to a two channel filter scheme, as shown by pass filter lines410 and 412, the signal from each label will produce a unique signalprofile between the two detection channels. In particular, signals arerouted through an optical train that includes two paths that arefiltered according to the spectral profile shown. For each signal,different levels of emitted light will pass through each path and bedetected upon an associated detector. The amount of signal that passesthrough each filter path is dictated by the spectral characteristics ofthe signal.

In the case of the above described mixed-mode schemes, detection systemsmay be provided that include at least two distinct detection channels,where each detection channel passes light within a spectrum that isdifferent from each other channel. Such systems also include a reactionmixture within optical communication of the detection channels, wherethe reaction mixture produces at least three different optical signalsthat each produces a unique signal pattern within the two detectionchannels, as compared to the other optical signals.

In each case, each signal-producing reactant is selected to provide asignal that is entirely distinct from each other signal in at least oneof signal intensity and signal channel. As noted above, signal intensityin a given channel is dictated, in part, by the nature of the opticalsignal, e.g., its emission spectrum, as well as the filters throughwhich that signal is passed, e.g., the portion of that spectrum that isallowed to reach the detector in a given channel. However, signalintensity can also be modulated by random variables, such as orientationof a label group when it is emitting signal, or other variables of theparticular reaction. Accordingly, for a signal's intensity to be assuredof being entirely different from the intensity of another signal withina given channel, in preferred aspects, this variation is accounted for.

With a reduced number of spectrally distinct signal events, thecomplexity of the optical paths for the integrated devices is alsoreduced. FIG. 5 illustrates a not-to-scale example device architecturefor performing optical analyses, e.g., nucleic acid sequencingprocesses, that rely in part on non-spectral discrimination of differingsignals, and optionally, in part on spectral distinction. As shown, anintegrated analytical device 500 includes a reaction region 502 that isdefined upon a first substrate layer 504. As shown, the reaction regioncomprises a well disposed in the substrate surface. Such wells mayconstitute depressions in a substrate surface or apertures disposedthrough additional substrate layers to an underlying transparentsubstrate, e.g., as used in zero mode waveguide arrays (See, e.g., U.S.Pat. Nos. 7,181,122 and 7,907,800).

In the device of FIG. 5, excitation illumination is delivered to thereaction region from an excitation light source (not shown) that may beseparate from or also integrated into the substrate. As shown, anoptical waveguide (or waveguide layer) 506 may be used to conveyexcitation light (shown by arrows) to the reaction region/well 502,where the evanescent field emanating from the waveguide 506 illuminatesreactants within the reaction region 502. Use of optical waveguides toilluminate reaction regions is described in e.g., U.S. Pat. No.7,820,983 and U.S. Patent Application Publication No. 2012/0085894,which are each incorporated by reference herein in their entireties forall purposes.

The integrated device 500 optionally includes light channelingcomponents 508 to efficiently direct emitted light from the reactionregions to a detector layer 512 disposed beneath the reaction region.The detector layer typically comprises one, or preferably multiple,detector elements 512 a-d, e.g., pixels in an array detector, that areoptically coupled to a given reaction region. Although illustrated as alinear arrangement of pixels 512 a-d, it will be appreciated that suchpixels may be arranged in a grid, n×n square, annular array, or anyother convenient orientation.

Emitted signals from the reaction region 502 that impinge on thesepixels are then detected and recorded. As noted above, an optionalsingle filter layer 510 is disposed between the detector layer and thereaction region, to permit different spectrally distinct signals totravel to different associated pixels 512 a and 512 b in the detectorlayer 512. For example, the portion 510 a of filter layer 510 allowssignals having a first emission spectrum to reach its associated pixels512 a and 512 b, while filter portion 510 b of filter layer 510 allowsonly signals having a distinct second spectrum to reach its associatedpixels 512 c and 512 d.

In the context of a sequencing system exploiting such a configuration,incorporation of two of the four nucleotides would produce signals thatwould be passed through filter portion 510 a to pixels 512 a and 512 b,and blocked by filter portion 510 b. As between these two signals, onesignal would have a signal intensity higher than the other such that thepixels 512 a and 512 b in detector layer 512 would be able to producesignal responses indicative of such differing signal intensities.Likewise, incorporation of the other two nucleotides would producesignals that would be passed through filter portion 510 b to itsassociated pixels 512 c and 512 d, while filter portion 510 a wouldblock those signals from reaching pixels 510 a and 510 b. Again, thesignals associated with these two latter signal events would differbased upon their signal intensities or amplitudes.

The detector layer is then operably coupled to an appropriate circuitry,typically integrated into the substrate, for providing a signal responseto a processor that is optionally included integrated within the samedevice structure or is separate from but electronically coupled to thedetector layer and associated circuitry. Examples of types of circuitryare described in U.S. Patent Application Publication No. 2012/0019828.

As will be appreciated from the foregoing disclosure and FIG. 5, theintegrated analytical devices described herein do not require the morecomplicated optical paths that are necessary in systems utilizingconventional four-color optics, obviating the need for excessive signalseparation optics, dichroics, prisms, or filter layers. In particular,although shown with a single filter layer, as noted, in optionalaspects, the filter layer could be eliminated or could be replaced witha filter layer that blocks stray light from the excitation source ratherthan distinguishing different emission signals from the reaction region.Even including the filter layer 510, results in simplified and/or moreefficient optics as compared to conventional four-color systems, whichwould require either multilayer filters, or narrow band pass filters,which typically require hybrid layers or composite approaches over eachsubset of pixels, thus blocking signal from reaching three of the fourpixel subsets at any given emission wavelength, resulting in detectionof far fewer photons from each signal event. The optics configurationshown in FIG. 5, on the other hand, only blocks a smaller portion of theoverall signal light from reaching the detector. Alternatively, suchconventional systems would require separation and differential directionof all four different signal types, resulting in inclusion of additionaloptical elements, e.g., prisms or gratings, to achieve spectralseparation.

FIG. 6 shows a schematic exemplar signal output for a real timesequencing operation using a two color/two amplitude signal set from anintegrated system of the invention where one trace (dashed) denotessignals associated with incorporation of A (high intensity signal) and T(lower intensity signal) bases, while the other signal trace (solidline), denotes the signals of a different emission spectrum, associatedwith G (high) and C (low) bases. The timing of incorporation and theidentity of the base incorporated, as derived from the color channel andintensity of the signal, are then used to interpret the base sequence.

Arrays of Integrated Optical Detection Devices

In order to obtain the volumes of sequence information that may bedesired for the widespread application of genetic sequencing, e.g., inresearch and diagnostics, higher throughput systems are desired. By wayof example, in order to enhance the sequencing throughput of the system,multiple complexes are typically monitored, where each complex issequencing a separate template sequence. In the case of genomicsequencing or sequencing of other large DNA components, these templateswill typically comprise overlapping fragments of the genomic DNA. Bysequencing each fragment, one can then assemble a contiguous sequencefrom the overlapping sequence data from the fragments.

As described above, and as shown in FIGS. 1A-1B, the template/DNApolymerase-primer complex of such a sequencing system is provided,typically immobilized, within an optically confined region, such as azero mode waveguide (ZMW), or proximal to the surface of a transparentsubstrate, optical waveguide, or the like. Preferably, such reactioncells are arrayed in large numbers upon a substrate in order to achievethe scale necessary for genomic or other large-scale DNA sequencingapproaches. Such arrays preferably comprise a complete integratedanalytical device, such as, for example, the devices shown in the blockdiagrams of FIGS. 2 and 5. Examples of integrated systems comprisingarrays of optical analytical devices are provided in U.S. PatentApplication Publication Nos. 2012/0014837; 2012/0019828; and2012/0021525.

Arrays of integrated analytical devices, such as arrays of devicescomprising ZMWs, can be fabricated at ultra-high density, providinganywhere from 1000 ZMWs per cm², to 10,000,000 ZMWs per cm², or more.Thus, at any given time, it may be desirable to analyze the reactionsoccurring in 100, 1000, 3000, 5000, 10,000, 20,000, 50,000, 100,000, 1Million, 5 Million, 10 Million, or more ZMWs or other reaction regionswithin a single analytical system or even on a single substrate.

In order to achieve the ultra-high density of ZMWs necessary for sucharrays, the dimensions of each ZMW must be relatively small. Forexample, the length and width of each ZMW is typically in the range offrom 50 nm to 600 nm, ideally in the range from 100 nm to 300 nm. Itshould be understood that smaller dimensions allow the use of smallervolumes of reagents and may, in some cases, help to minimize backgroundsignals from reagents outside the reaction zone and/or outside theillumination volume. Accordingly, in some embodiments, the depth of theZMW may be in the range of 50 nm to 600 nm, more ideally in the range of100 nm to 500 nm, or even more ideally in the range of 150 to 300 nm.

It should also be understood that shape of the ZMW will be chosenaccording to the desired properties and methods of fabrication. Forexample, the shape of the ZMW (e.g., when viewed from above the ZMW, forexample as from the top of the drawings in FIGS. 2 and 5) may becircular, elliptical, square, rectangular, or any other desired shape.Furthermore, the walls of the ZMW may be fabricated to be vertical, forexample as shown in the reaction cells of FIGS. 2 and 5. Alternatively,the walls of the ZMW may be fabricated to slope inward or outward if sodesired. In the case of a circular ZMW, an inward or outward slope wouldresult in, for example, a cone-shaped or inverted cone-shaped ZMW.

Using the foregoing systems, simultaneous targeted illumination ofthousands or tens of thousands of ZMWs in an array has been described.However, as the desire for multiplex increases, the density of ZMWs onan array, and the ability to provide targeted illumination of sucharrays, increases in difficulty, as issues of ZMW cross-talk (signalsfrom neighboring ZMWs contaminating each other as they exit the array),decreased signal:noise ratios arising from higher levels of denserillumination, and the like, increase. The devices and methods of theinstant invention address some of these issues.

The position on the detector upon which a given signal is incident isindicative of (1) the originating ZMW in the array, and (2) the emissioncharacteristics of the signal component, which is used, for example, toidentify the type of fluorescently labeled nucleotide analogincorporated in an extension reaction. As noted above, the detector mayinclude in some cases multiple sensing elements, each for detectinglight having a different color spectrum. For example, in the case ofsequencing, the sensor for each reaction cell may have 4 elements, onefor each of the four bases. In some cases, the sensor elements providecolor discrimination, in other cases, color filters are used to directthe appropriate color of light to the appropriate sensor element. Insome cases, the sensor elements detect intensity of signal only, withoutdiscriminating color. In some cases, the sensor elements identifies theincorporated nucleotide using a combination of emission characteristics.

Optical Waveguides

As mentioned above, the analytical devices of the instant invention, insome embodiments, comprise an optical waveguide to deliver excitationenergy to a sample. For example, as shown in FIG. 5, optical waveguide506 conveys excitation light to the reaction region/well 502, where theevanescent field emanating from the waveguide 506 illuminates reactantswithin the reaction region 502. The use of an optical waveguide todeliver excitation illumination is advantageous for numerous reasons.For example, because the illumination light is applied in a spatiallyfocused manner, e.g., confined in at least one lateral and oneorthogonal dimension, using efficient optical systems, e.g., fiberoptics, waveguides, multilayer dielectric stacks (e.g., dielectricreflectors), etc., the approach provides an efficient use ofillumination (e.g., laser) power. For example, illumination of asubstrate comprising many separate reaction sites, “detection regions,”or “observation regions” using waveguide arrays as described herein canreduce the illumination power ˜10- to 1000-fold as compared toillumination of the same substrate using a free space illuminationscheme comprising, for example, separate illumination (e.g., via laserbeams) of each reaction site. In general, the higher the multiplex(i.e., the more surface regions to be illuminated on the substrate), thegreater the potential energy savings offered by the waveguideillumination schemes provided herein. In addition, since waveguideillumination need not pass through a free space optical train prior toreaching the surface region to be illuminated, the illumination powercan be further reduced.

In addition, because illumination is provided from within confinedregions of the substrate itself (e.g., optical waveguides), issues ofillumination of background or non-relevant regions, e.g., illuminationof non-relevant materials in solutions, autofluorescence of substrates,and/or other materials, reflection of illumination radiation, etc., aresubstantially reduced.

In addition to mitigating autofluorescence of substrate materials, thesystems described herein substantially mitigate autofluorescenceassociated with the optical train. In particular, in typicalfluorescence spectroscopy, excitation light is directed at a reaction ofinterest through at least a portion of the same optical train used tocollect signal fluorescence, e.g., the objective and other optical traincomponents. As such, autofluorescence of such components will contributeto the detected fluorescence level and can provide signal noise in theoverall detection. Because the systems provided herein direct excitationlight into the substrate through a different path, e.g., through anoptical fiber optically coupled to the waveguide in the substrate, thissource of autofluorescence is eliminated.

Waveguide-mediated illumination is also advantageous with respect toalignment of illumination light with surface regions to be illuminated.In particular, substrate-based analytical systems, and particularlythose that rely upon fluorescent or fluorogenic signals for themonitoring of reactions, typically employ illumination schemes wherebyeach analyte region must be illuminated by optical energy of anappropriate wavelength, e.g., excitation illumination. While bathing orflooding the substrate with excitation illumination serves to illuminatelarge numbers of discrete regions, such illumination may suffer from themyriad complications described above. To address those issues, targetedexcitation illumination may serve to selectively direct separate beamsof excitation illumination to individual reaction regions or groups ofreaction regions, e.g. using waveguide arrays. When a plurality, e.g.,hundreds or thousands, of analyte regions are disposed upon a substrate,alignment of a separate illumination beam with each analyte regionbecomes technically more challenging and the risk of misalignment of thebeams and analyte regions increases. Alignment of the illuminationsources and analyte regions may be built into the system, however, byintegration of the illumination pattern and reaction regions into thesame component of the system, e.g., a waveguide substrate. In somecases, optical waveguides may be fabricated into a substrate at definedregions of the substrate, and analyte regions are disposed upon thearea(s) of the substrate occupied by the waveguides.

Finally, substrates used in the waveguides may be provided from ruggedmaterials, e.g., silicon, glass, quartz or polymeric or inorganicmaterials that have demonstrated longevity in harsh environments, e.g.,extremes of cold, heat, chemical compositions, e.g., high salt, acidicor basic environments, vacuum and zero gravity. As such, they providerugged capabilities for a wide range of applications.

Waveguide substrates used in the devices and methods of the presentinvention generally include a matrix, e.g., a silica-based matrix, suchas silicon, glass, quartz or the like, polymeric matrix, ceramic matrix,or other solid organic or inorganic material conventionally employed inthe fabrication of waveguide substrates, and one or more waveguidesdisposed upon or within the matrix, where the waveguides are configuredto be optically coupled to an optical energy source, e.g., a laser. Suchwaveguides may be in various conformations, including but not limited toplanar waveguides and channel waveguides. Some preferred embodiments ofthe waveguides comprise an array of two or more waveguides, e.g.,discrete channel waveguides, and such waveguides are also referred toherein as waveguide arrays. Further, channel waveguides can havedifferent cross-sectional dimensions and shapes, e.g., rectangular,circular, oval, lobed, and the like; and in certain embodiments,different conformations of waveguides, e.g., channel and/or planar, canbe present in a single waveguide substrate.

In typical embodiments, a waveguide comprises an optical core and awaveguide cladding adjacent to the optical core, where the optical corehas a refractive index sufficiently higher than the refractive index ofthe waveguide cladding to promote containment and propagation of opticalenergy through the core. In general, the waveguide cladding refers to aportion of the substrate that is adjacent to and partially,substantially, or completely surrounds the optical core. The waveguidecladding layer can extend throughout the matrix, or the matrix maycomprise further “non-cladding” layers. A “substrate-enclosed” waveguideor region thereof is entirely surrounded by a non-cladding layer ofmatrix; a “surface-exposed” waveguide or region thereof has at least aportion of the waveguide cladding exposed on a surface of the substrate;and a “core-exposed” waveguide or region thereof has at least a portionof the core exposed on a surface of the substrate. Further, a waveguidearray can comprise discrete waveguides in various conformations,including but not limited to, parallel, perpendicular, convergent,divergent, entirely separate, branched, end-joined, serpentine, andcombinations thereof.

A surface or surface region of a waveguide substrate is generally aportion of the substrate in contact with the space surrounding thesubstrate, and such space may be fluid-filled, e.g., an analyticalreaction mixture containing various reaction components. In certainpreferred embodiments, substrate surfaces are provided in apertures thatdescend into the substrate, and optionally into the waveguide claddingand/or the optical core. In certain preferred embodiments, suchapertures are very small, e.g., having dimensions on the micrometer ornanometer scale, as described further below.

It is an object of devices and methods of the invention to illuminateanalytes (e.g., reaction components) of interest and to detect signalemitted from such analytes, e.g., by excitation and emission from afluorescent label on the analyte. Of particular interest is the abilityto monitor single analytical reactions in real time during the course ofthe reaction, e.g., a single enzyme or enzyme complex catalyzing areaction of interest. The waveguides described herein provideillumination via an evanescent field produced by the escape of opticalenergy from the optical core. The evanescent field is the optical energyfield that decays exponentially as a function of distance from thewaveguide surface when optical energy passes through the waveguide. Assuch, in order for an analyte of interest to be illuminated by thewaveguide, it must be disposed near enough to the optical core to beexposed to the evanescent field. In preferred embodiments, such analytesare immobilized, directly or indirectly, on a surface of the waveguidesubstrate. For example, immobilization can take place on asurface-exposed waveguide, or within an aperture in the substrate. Insome preferred aspects, analyte regions are disposed in apertures thatextend through the substrate to bring the analyte regions closer to theoptical core. Such apertures may extend through a waveguide claddingsurrounding the optical core, or may extend into the core of thewaveguide.

In certain embodiments, such apertures also extend through a mask layerabove the surface of the substrate. In preferred embodiments, suchapertures are “nanoholes,” which are nanometer-scale holes or wells thatprovide structural confinement of analytic materials of interest withina nanometer-scale diameter, e.g., ˜10-100 nm. In some embodiments, suchapertures comprise optical confinement characteristics, such aszero-mode waveguides, which are also nanometer-scale apertures and arefurther described elsewhere herein. Although primarily described hereinin terms of channel waveguides, such apertures could also be constructedon a planar waveguide substrate, e.g., where the planar waveguideportion/layer is buried within the substrate, i.e., is notsurface-exposed. Regions on the surface of a waveguide substrate thatare used for illumination of analytes are generally termed “analyteregions”, “reaction regions”, or “reaction sites”, and are preferablylocated on a surface of the substrate near enough to an optical core tobe illuminated by an evanescent wave emanating from the optical core,e.g., on a surface-exposed waveguide or at the bottom of an aperturethat extends into the substrate, e.g., into the waveguide cladding orcore. The three-dimensional volume at a reaction site that isilluminated by the evanescent field of a waveguide core (e.g., to anextent capable of allowing detection of an analyte of interest) isgenerally termed the “observation volume” or “illumination volume”. Aregion of a waveguide substrate that comprises one or more analyteregions is generally referred to as a “detection region” of thesubstrate, and a single substrate may have one or multiple detectionregions. Examples of such optical waveguides are provided in in U.S.Pat. No. 7,820,983 and U.S. Patent Application Publication No.2012/0085894, as described above.

The present invention provides devices for waveguide-based illuminationof analyte regions in apertures (e.g., nanoholes or ZMWs) that in somecases reduce the variation in illumination, for example, by mitigatingpropagation losses over the length of the waveguide. Such propagationlosses can be further exacerbated by a metal layer disposed over thesurface of the substrate, because it can absorb optical energy from asurface-exposed or core-exposed waveguide, or even a waveguide near tothe surface of the substrate. Such metal layers are typically found inconventional ZMW arrays, presenting a challenge for combining sucharrays with waveguide illumination strategies.

One of the limitations of waveguide illumination is optical attenuationas the light propagates down the guide resulting in a reduction in powerat different locations in the guide. For example, a particular laserintensity coupled into the waveguide will experience a slow decrease inenergy density as light travels down the guide due to propagationlosses, with the highest power at the end nearest the illuminationsource and the lowest at the end farthest from the illumination source.The degree of the propagation loss is typically a function of thedesigned geometry and manufacturing tolerances, and presents a challengeto performing multiplexed analytical reactions because it constrains thespatial range of the usable waveguide structure. It is important tomaximize the distance over which the laser intensity is sufficientlyuniform, in order to maximize the multiplex capabilities of the system.It is therefore an object of the present invention to provide uniformpower over the length of a waveguide, e.g., to promote uniformillumination of all reaction sites to be illuminated by the waveguide.

In this context, it should be understood that light may be propagatedfrom either direction within a waveguide, and that propagation of lightfrom each end of a waveguide simultaneously may in some circumstanceshelp to mitigate propagation losses within the waveguide. In somecircumstances it may be advantageous to propagate light from each end ofa waveguide sequentially, rather than simultaneously, as would beunderstood by those of ordinary skill in the art.

In certain embodiments, a waveguide is tapered such that the coregradually becomes thinner along the direction of propagation. Thiscauses the degree of light confinement to be gradually increased, whichcan offset the gradual reduction in the total amount of power in theguide due to propagation losses and essentially maintain a desired modeshape and field strength for the optical energy propagated over thelength of the waveguide core. In principle, the sum of propagationlosses is balanced by the decreasing core size such that uniformity ofevanescent field strength can be held constant for an arbitrarily longdistance, with limitations to the strength of the evanescent field alsobeing dependent on the starting laser power and the starting waveguidecore dimensions. For a given waveguide substrate, once the propagationloss is determined the waveguide geometry can be designed to smoothlyvary, thereby modifying the degree of confinement such that the relativefield strength at the point of interest increases at the same rate thatpropagation losses reduce the total power in the guide. For example, atapered waveguide core can be widest at the portion most proximal to thelight source, slowly narrowing along the guide, with the fieldlocalization increasing at the same rate that propagation losses arereducing the waveguide field strength. The tapering can take place inany direction including the z direction (top to bottom), the y direction(side to side), or a combination thereof.

In certain embodiments, a waveguide cladding above a waveguide core in awaveguide substrate is tapered such that the waveguide core is slowlybrought closer to the reaction sites at the surface of the substrate byan ever-decreasing width of the waveguide cladding layer that separatesthe core from the reaction sites. As such, although there is propagationloss from the waveguide, as the field strength in the waveguidedecreases, it is brought closer to the reaction sites, and thisincreasing proximity compensates for an overall reduced field strength.In some embodiments, both the waveguide cladding layer and waveguidecore are tapered to mitigate loss of field strength due to propagationlosses.

Local Field Enhancement

In certain embodiments, the waveguides used in some of the devicesdisclosed herein comprise a specific feature associated with eachaperture, a local field enhancement element, to increase the efficiencyof sample illumination. Such a feature serves to improve the couplingefficiency between the waveguide and the illumination volume,particularly when the apertures are subwavelength apertures in a metallayer disposed over the surface of the substrate. For example, in someembodiments, the local field enhancement element is a layer of amaterial in the vicinity of each aperture that has a higher dielectricconstant than the cladding layer or that is a metal, such as, forexample, copper, silver, gold, or aluminum. One example of this type oflocal field enhancement element is shown in FIG. 7A, where the localfield enhancement element corresponds to a ring or other geometricpattern of high dielectric material or metal 706 surrounding theaperture 702, just below the opaque, metal layer 704. As shown in FIG.7A, a pattern of high dielectric material, such as Al₂O₃, or a metal,couples energy from the waveguide core of high refractive index 708,such as Si₃N₄, through the cladding of low refractive index 710, such asSiO₂. Other suitable materials of high dielectric material may besubstituted for Al₂O₃, as would be understood by those of ordinary skillin the art.

The material of high dielectric or metal surrounding the aperture mayserve other purposes in addition to improving the coupling of excitationlight to the illuminated volume within the aperture. For example, ifthis material is deposited such that it is exposed to the solution to beanalyzed, it may act as a distinct surface for immobilization ofbiomaterials or to prevent immobilization of those materials.Specifically, there may be advantages in providing different surfaces onthe bottom and sides of the aperture to allow, for example, for biasedimmobilization of reaction components. See, e.g., U.S. PatentPublication No. 2012/0085894. For example, as shown in FIG. 7A, thesides of the nanowell/aperture may expose a material such as, e.g., thehigh dielectric material or the metal, whereas the bottom of thenanowell/aperture may expose the cladding material, e.g., glass.Selective deposition of analytes is preferably effected when there arechemical differences between the surfaces, as would be understood bythose of ordinary skill in the art.

The local field enhancement element may include additional features tofurther enhance the efficiency of sample illumination by excitationlight, to further decrease propagation losses of excitation light, or toprovide other functions, such as, for example, enhancing the detectionof light emitted from the sample. One such additional feature isexemplified in FIG. 7B, where a pattern of high dielectric material ormetal 726 surrounds the nanowell/aperture 722 below the opaque, metallayer 724. These patterns, for example a pattern of concentric ringssurrounding the aperture, as shown in FIG. 7B, may act as a broad areacoupler for the excitation light into the sample volume. They mayadditionally act to collimate light emitted from sample in theilluminated volume within the aperture, thus improving the detectabilityof that light. In this particular embodiment, the local enhancementelement thus serves to couple light both into and out of the aperture.Also shown in FIG. 7B is the waveguide core of high refractive index728, such as Si₃N₄, set within the cladding of low refractive index 730,such as SiO₂.

Aperture shapes, and the shape of the high dielectric material or metalsurrounding the apertures, may additionally enhance the coupling oflight energy from the waveguide core to the illuminated volume. See, forexample, Sahin et al. (2011) J. Nanophoton. 5(1), 051812;doi:10.1117/1.3599873. Subwavelength aperture shapes, including C-shapedapertures, triangle pairs, or diamond-shaped aperture structures mayaccordingly be usefully employed as local field enhancement elementsaccording to this aspect of the invention.

In yet another embodiment, the local field enhancement elementcorresponds to increasing the thickness of the cladding in the regionsof the waveguide that are not adjacent to the aperture and/or decreasingthe thickness of the cladding in the regions of the waveguide that areadjacent to the aperture. This embodiment provides, for example, fordecreased propagation losses, due to the increased distance between thelight beam and the metallic layer, and for increased couplingefficiency, due to the positioning of the aperture closer to theevanescent wave. As shown in FIG. 7C, decreasing the thickness of thecladding 750 (e.g., SiO₂) in the region around the aperture 742 byrecessing the aperture improves the coupling of light energy into theillumination volume. Increasing the thickness of the cladding in regionsremote from the aperture decreases propagation losses resulting frominteractions of the evanescent wave with the opaque metallic layer 744.FIG. 7C also shows an additional optional local field enhancementelement in the form of a ring of high dielectric material or metal 746surrounding the aperture below the opaque metallic layer. As notedabove, this element can be a ring or other pattern of high dielectricmaterial or metal in the vicinity of the aperture, just below the opaquemetallic layer. Combinations of different local field enhancementelements may thus provide synergistic improvements in the coupling oflight energy from the waveguide core to the illuminated volume and areconsidered within the scope of the invention. Also shown in FIG. 7C isthe waveguide core of high refractive index 748, such as Si₃N₄, setwithin the cladding of low refractive index 750.

FIGS. 8A and 8B illustrate top-down and cross-sectional views of anotherembodiment of the analytical device, similar to the device of FIG. 7C,in which the aperture is surrounded by a ring of high dielectric ormetal 806 and is recessed to bring it closer to the waveguide core.(Note that the opaque, metallic layer 804 is omitted from the top-downview shown in FIG. 8A.) This embodiment also includes an additionaloptional feature of this aspect of the invention, a stray-lighttermination element 812. Such a design feature can decrease backgroundsignal by blocking scattered light from the excitation source andpotentially also autofluorescence from materials within the device. Thematerial used in the stray-light termination element is selected frommaterials that selectively absorb light to be blocked from reaching thedetector layer of the device, as would be understood by one of ordinaryskill in the art. Also shown in FIGS. 8A and 8B is the waveguide core ofhigh refractive index 808, such as Si₃N₄, set within the cladding of lowrefractive index 810, such as SiO₂. Exemplary dimensions for the deviceare indicated in FIG. 8A.

FIGS. 9A-9C illustrate a device configuration used in a mathematicalsimulation of the effectiveness of the above designs, specificallyincreasing the cladding thickness in regions not adjacent to theaperture and including a ring of metal 906 in the vicinity of theaperture. (Note that the opaque, metallic layer 904 is omitted from thetop-down view shown in FIG. 9A.) In particular, the simulations involvea finite-difference time-domain (FDTD) solution of the Maxwellequations. See Taflove and Hagness (2004) Computational Electrodynamics:The Finite-Difference Time-Domain Method, Third Edition. FIGS. 9A-9Calso show the waveguide core of high refractive index 908, such asSi₃N₄, set within the cladding of low refractive index 910, such asSiO₂.

The simulations using the device configuration of FIGS. 9A-9Cdemonstrate that by increasing the cladding thickness between ZMWs by200 nm, the propagation loss, for example, due to proximity to themetallic layer, decreases from over 100 dB/mm to ˜14 dB/mm, allowing alower laser power to illuminate several ZMWs. Overall illuminationefficiency of the fluorophore is kept high, so as to keep the totallaser power in the waveguide low, thus helping to limit autofluorescencegenerated in the waveguide. In addition, a metal ring (or cylindricalshell) in the vicinity of the aperture provides enough metal to enhancethe coupling to the ZMW but not so much as to create waveguide loss.While any metal could be used, metals such as copper, silver, gold, andaluminum are preferred. Typical metal thicknesses (i.e., shellthickness) around the aperture are 100-400 nm. Since aperture diametersare preferably in the range of 100-200 nm, and most preferablyapproximately 140 nm, the outer diameter of the metal ring is thereforepreferably from 340 nm to 1 μm, although outer ring diameters of fromabout 0.2 to 2 μm, or even higher, are contemplated.

Dimensional Modulation of Waveguides

As noted above, efficient coupling of excitation light into theillumination volume requires that the optical waveguide be sufficientlyclose to the nanometer-scaled apertures, but placement of the opticalwaveguide too close to the metallic layer in which the apertures aredisposed may cause propagation losses. In order to overcome theselimitations, in another aspect of the invention, the optical waveguideis placed sufficiently far from the metallic layer to avoid propagationlosses, and the cross-sectional area of the waveguide is modulated inthe vicinity of the apertures to enlarge the mode size and thus increasethe coupling of light into the illuminated volume. In general, waveguidecore dimensions are designed to satisfy the single-mode condition, aswell as confining the mode compactly around the core region. Inpreferred embodiments, the cross-sectional area of the optical core isdecreased at locations where the optical waveguide illuminates theapertures. In some embodiments, the decrease in cross-sectional area ofthe optical core is achieved using adiabatic tapers in order to avoidextra power loss. In preferred embodiments, and as illustrated in FIGS.10A and 10B, the thickness of the optical waveguide is kept constant,while the cross-sectional area of the optical core is modulated byvarying the width of the optical core. Specifically, FIG. 10A provides atop-down view of waveguide 1008 with cross-sectional views of a normalsection of the waveguide with compact mode size (left cross-section) anda tapered-down section of the waveguide with expanded mode size (rightcross-section). FIG. 10B provides a three-dimensional perspective of theexemplary device showing locations of nanowell/apertures 1002 within theopaque, metal layer 1004 covering the array. Also shown aredimension-modulated waveguides 1008 positioned below thenanowell/apertures. Fabrication of the core layer in this embodiment issimplified, because the core thickness is uniform. In some embodiments,the optical signal passing through the waveguide core is transverseelectric (TE) polarized light. These embodiments provide advantages whenthe cross-sectional area of the waveguide is modulated by varying thewidth of the waveguide core, because the mode size of TE-polarized lightis most strongly affected by the waveguide width.

In variants of the just-described aspect of the invention, the width ofthe optical waveguide is kept constant, while the cross-sectional areaof the optical core, and thus the mode size of the transmitted light, ismodulated by varying the thickness of the optical core. As above, thecross-sectional area of the optical core is decreased at locations wherethe optical waveguide illuminates the apertures in order to maximizecoupling to the illuminated volume. In some embodiments, the opticalsignal passing through the waveguide core is transverse magnetic (TM)polarized light, since the mode size of TM-polarized light is moststrongly affected by the waveguide thickness, as would be understood byone of ordinary skill in the art.

In some embodiments of the invention, dimensional modulation of thewaveguides and local field enhancements may be usefully combined. Forexample, modulation of the cross-sectional area of the optical core ateach aperture may be usefully combined with a pattern of high dielectricmaterial or metal in the vicinity of each aperture, for example, belowthe metallic layer. Such combinations provide yet further improvement inthe efficiency of coupling of optical energy from the waveguide to theilluminated volume.

By way of non-limiting example, the typical waveguide widths for use inthe analytical devices of the instant invention range from 100 nm to1000 nm. Such widths therefore correspond to roughly 0.3 to 3.0wavelengths in a situation where the wavelength of excitation lightpropagated along the waveguide is 335 nm. (It should be noted that thewavelength of photons in a waveguide may be significantly shifted fromthat of the same photons traveling through air.) In some embodiments ofthe invention, the width of the waveguide optical core is decreased by 5to 90% at locations where the evanescent field illuminates thenanometer-scale apertures, compared to locations where the evanescentfield does not illuminate the apertures (in other words, the opticalcore is decreased from 0.15 wavelengths to 2.7 wavelengths for a corethat is 3.0 wavelengths wide). In some embodiments, the width of thewaveguide optical core is decreased by 5 to 50% at locations where theevanescent field illuminates the apertures, compared to locations wherethe evanescent field does not illuminate the apertures (i.e., from 0.15wavelengths to 1.5 wavelengths in a 3.0 wavelength wide core). Inpreferred embodiments, the width of the waveguide optical core isdecreased by 10 to 20% at those locations (i.e., from 0.30 wavelengthsto 0.60 wavelengths). As noted above, it is desirable in the devices ofthis aspect of the invention for the changes in width/cross-sectionalarea to be gradual, preferably adiabatic, in order to avoid anadditional mechanism for propagation losses. Such gradualtapering—narrower in the locations near the nanometer-scale aperturesand wider in the locations away from the nanometer-scale apertures—canbe readily be optimized in the design of the device, using analyticalcalculations, as would be understood by one of ordinary skill in theart.

Waveguide Core Positioning

In another aspect of the invention, the configuration and positioning ofthe waveguide core is varied in order to maximize collection of signalphotons while suppressing collection of background photons (e.g.,scattered light and autofluorescence). In particular, in theseembodiments the waveguide core is positioned so that it is not directlybetween the nanometer-scaled apertures and their correspondingdetectors. In preferred embodiments, the illuminated volume in eachaperture is illuminated by evanescent fields emanating from two or moreoptical cores. In some embodiments, the device further contains anopaque layer disposed between the waveguide layer and the detectorlayer. The opaque layer contains a plurality of openings positioned toallow signal photons from the sample to pass unimpeded into thedetector. The opaque layer would thus decrease access of photons from,for example, autofluorescence or scattering emanating from the waveguidecores, to the detector, and thus decrease background signal. As would beunderstood by one of ordinary skill in the art, signal photon collectionis defined by photon flux through the opening in the opaque material,and collection efficiency is modulated by the dimensions of the openingand the optical distance from the signal source. Likewise, collection ofautofluorescence and scattered light from the waveguide core through theopening is governed by the dimensions of the opening and the solid angleoccupied by the waveguide as viewed from the opening.

By using a waveguide that is not positioned directly between thenanometer-scaled aperture and the detector, i.e., a “slot” waveguide,the waveguide core, and associated autofluorescence and scattering, ismoved away from a direct path to the detector, thus increasing the angleof incidence into the detector and decreasing background signal.Furthermore, slot waveguides may provide increased optical fields in theregions of low refractive index between the high-index cores, and thusincrease coupling of optical energy from the waveguides to theilluminated volume. See, for example, Feng et al. (2006) IEEE J. QuantumElectron. 42, 885; Sun et al. (2007) Optics Express 15, 17967. Opticalsensing devices making use of slot waveguides have been described. See,for example, Barrios (2006) IEEE Photon Technol. Lett. 18, 2419; Barrioset al. (2007) Optics Letters 32, 3080; Barrios et al. (2008) OpticsLetters 33, 708; Robinson et al. (2008) Optics Express 16, 4296. Thesignal-to-background ratio in devices of the instant invention thatutilize a slot waveguide format may be optimized, for example, byvarying the dimension of the openings in the opaque layer and by varyingthe configuration of the waveguide (e.g., spacing between separateoptical cores and distance between waveguide core, opaque layer, anddetector layer), as would be understood by those of ordinary skill inthe art.

FIGS. 11A-11B illustrate an example of this aspect of the invention thatincludes an optional local field enhancement element to increase furtherthe coupling of excitation energy to the illuminated volume. Inparticular, FIG. 11A, illustrates a cross-sectional view of the devicedown the length of the divided (i.e., “slot”) waveguide cores 1108,surrounded by cladding of low refractive index 1110. As shown, theevanescent waves emanating from the separate cores overlap and jointlyilluminate the sample “signal source” 1103 within a nanowell/aperture atthe top of the drawing. The local field enhancement element 1106 isillustrated in this drawing as a rectangle below the sample. Thiselement could, for example, correspond to a material of high dielectricconstant or metal patterned in the area adjacent to the nanometer-scaleapertures, as described above. As also described more fully above, thiselement serves to increase coupling between the waveguide core and thesample within the nanometer-scale apertures and thus increase signalemission from the sample. Such increased coupling could further increasethe signal-to-background ratio in the devices of the invention bydecreasing the size of the field necessary in the core and thusdecreasing the associated autofluoresence and scattering.

FIG. 11A further illustrates the opaque layer 1114, which is positionedbetween the waveguide layer and the detector 1118, and the opening inthe opaque layer to allow emission signal from the illuminated volume topass to the detector. The opaque layer is fabricated from any materialsuitable for attenuating transmission of excited light from thewaveguide core to the detector, e.g., a metal layer of sufficientthickness. As shown in 11A, the positioning of the waveguide cores awayfrom a direct alignment between the nanometer-scale aperture (not shown,but surrounding the illuminated sample volume) and the detector does notgreatly diminish the efficiency of excitation of the illuminated volume,particularly if an optional local enhancement element is included toenhance the coupling, but causes a significant decrease in thetransmission of autofluorescence or scattered light to the detector, dueto the presence of the opaque layer.

FIG. 11B provides a top-down view of the analytical device shown in FIG.11A, including the divided waveguide cores 1108. The “signal source”1103, which corresponds to the illuminated volume of the sample is abovethe plane of the drawing, and the opaque layer, including the “opening”1116 in the opaque layer over the detector is below the plane of thedrawing. The local enhancement element 1106 is illustrated as arectangular block, but any of the local enhancement elements describedabove could usefully be included in the device to enhance coupling ofexcitation energy to the sample volume. The detector is not shown inthis drawing but would be positioned below the opening and in line withthe signal source.

Waveguide Frequency Conversion

As noted above, excitation light is typically provided to sample volumesvia guided optics. Part of the motivation for this approach lies in thepossibility of dispensing with the disadvantages of classic free-spaceoptics by directing the sum total of excitation light needed to excitethe illumination volumes in all of the nanometer-scale apertures througha single optical system and onto a single chip. The guided opticalapproach can involve some disadvantages of its own, however, includingalignment complexity, cumulative autofluorescence, scattering, andcumulative laser heating. The latter three issues in particular arestraightforward limitations that result from the material properties ofthe optical system. The traditional chemistry and chemical formulationsused in fluorescence-based nucleic acid sequencing contribute to thedifficulties, as photonic excitation must be delivered within a fairlynarrow range of wavelengths, and the resulting emission wavelengths areonly slightly longer. Consequently, autofluorescence of the systemgenerally occurs within the same region of the spectrum as the desiredfluorescence emission signals and can therefore be a significantlimitation on the optical signal-to-noise ratio that can be achieved ina given system. Scattering can also be a detriment to signal-to-noise,because it is difficult to control the direction that scattered lighttravels as it leaves the guided mode, and some fraction may arrive at asensor, adding noise. Such scattered light may be difficult to filterout based on its wavelength. Similarly, photonic heating caused bynon-negligible absorption of the materials used to construct the opticalsystem and the sample chip is a strong function of the excitationwavelength, and there is little flexibility in altering this parametergiven the limitations in reagents used in typical sequencing reactions.

Accordingly, in another aspect of the invention, the limitations of atypical multiplexed sequencing system are addressed by using opticaltechniques such as harmonic generation, four-wave mixing, and stimulatedraman scattering to manipulate the wavelengths of pump excitation awayfrom those necessary for sample illumination and detection and towardspectral regions that are more suitable for the optical system,particularly with respect to the effects of the excitation photons onautofluorescence, laser heating, propagation loss, signal-to-backgroundratios, etc. Specifically, it is generally beneficial for excitationlight to be transported as longer-wavelength photons, for example asinfrared photons, which generate less autofluorescence within the deviceand which result in less laser heating. Shorter-wavelength light can begenerated at predetermined locations, as desired, preferably only in thelocations necessary to excite the relevant samples. Waveguide frequencyconversion can be effected by only slight modifications in opticalparameters through phase matching, or it can be actively switched on andoff through electro-optical effects that modify the refractive index ofone or more materials. Thus, light can be transported as an infraredpump and then be efficiently coupled into shorter wavelength harmonicwaveguide modes as desired. An additional advantage of such delivery ofwaveguide light is that scattering of light is dramatically reduced,because the infrared pump wavelength is significantly different inwavelength from the signal being collected by the detector, therebyreducing the detrimental impact of scattering on the signal-to-noiseratio.

Wavelength conversion in waveguides is typically effected through secondharmonic generation (SHG), wherein efficient conversion involves threefeatures: a nonlinear optical (NLO) material (in the case of SHG, forexample, a noncentrosymmetric material that responds to electromagneticfields with higher polarization multipoles), phase matching (typicallywith equal group velocities on both propagating modes), and sufficientoverlap integral (for example, where the energy density overlaps betweenthe fundamental mode, the harmonic mode, and the nonlinear material inthe structure). All three features can be designed into a waveguidestructure, and all three can be selected or adjusted by a variety oftechniques that are well understood by those of ordinary skill in theart. Furthermore, the techniques are widely available and are alreadybeing used in numerous commercial applications. In addition to SHG,similar techniques have been applied to other nonlinear opticalinteractions including optical parametric amplification (OPA) andstimulated Raman scattering. Such alternative approaches should also beconsidered within the scope of the instant invention.

At a fundamental level, periodic poling may be used to determine wherelight is converted from longer wavelengths, for example infraredwavelengths, to wavelengths usefully utilized in the direct excitationof samples, for example visible wavelengths. Such periodic poling may bedivided generally into two branches, a fixed periodic poling, whichwould not change in time, and a dynamic periodic poling, which can beused to fine-tune the wavelength conversion and to switch on or off theconversion at any location or set of locations, and at any time. Theprogrammability of such approaches is of particular value in theapplication of periodic poling to wavelength conversion for use in thesequencing methods described herein. Application of these techniques,including, for example, materials used, methods of fabrication, opticalproperties, theoretical principles, methods of tuning, conversionefficiencies, and so forth, are known in the art. See, for example, Yaoand Wang, Quasi-Phase-Matching Technology, in Nonlinear Optics andSolid-State Lasers, Springer Series in Optical Sciences 164,Springer-Verlag Berlin Heidelberg 2012. Specific examples of the use offixed and dynamic periodic poling in wavelength conversion devices havealso been reported. See Laurell et al. (2012) Optics Express 20, 22308;Chen et al. (2012) Optics Letters 37, 2814; Nava et al. (2010)Electronics Letters 46, 1686; Pan et al. (2010) Optics Communications284, 429.

An example of a basic SHG waveguide usefully employed in the devices ofthe instant invention is illustrated in FIG. 12A, where the nonlinearmedium is present in the core material of the waveguide, thussimplifying the overlap integral. An alternative structure, wherein thenonlinear medium is present in part of the cladding material, is shownin FIG. 12B.

FIG. 13A illustrates phase matching by periodic NLO materials. Such anapproach can allow significantly relaxed fabrication tolerances comparedto situations where phase matching is not provided by such periodicity.FIG. 13B illustrates phase modulation by electro-optic effects. Itshould be noted in this context that virtually all SHG materials alsoexhibit the strong Pockels coefficients that are important for thiselectro-optical effect.

The approaches for waveguide frequency conversion described herein canbe incorporated into the architecture of an analytical device in avariety of ways. For example, as shown in FIG. 14A, SHG conversion maytake place just after light is coupled into the chip. Alternatively, orin addition, excitation light may be injected into the waveguide andconverted into SHG at predetermined locations, as shown in FIG. 14B. Insome embodiments, excitation light can be programmed such that differentregions of nanometer-scale apertures and their corresponding illuminatedvolumes can be switched on and off independently.

Integrated Illumination

As described above, the analytical devices disclosed herein may be usedto monitor single molecule real time sequencing reactions, wherein atemplate/polymerase primer complex is provided, typically immobilized,within an optically confined region, such as within a nanometer-scaleaperture, e.g., a ZMW, nanohole, or “nanowell”, or proximal to thesurface of a transparent substrate. The optically confined region isilluminated with an excitation radiation appropriate for thefluorescently-labeled nucleotides that are to be used. Because thecomplex is within an optically confined region, or very smallillumination volume, only the reaction volume immediately surroundingthe complex is subjected to the excitation radiation.

Although the integrated analytical devices of the instant inventioninclude, in some aspects, waveguides to provide the necessaryillumination for monitoring these reactions from an external source, inanother aspect, the source of illumination may, alternatively, or inaddition, be provided by one or more illumination elements integrateddirectly into the device, such that the integrated illumination elementoptically excites a single nanowell or a subset of nanowells, eitherdirectly or in combination with a lateral waveguide. Such integratedillumination elements are generally useful for interrogating singlemolecule events, as they may break adverse scaling behavior orperformance in highly multiplexed systems and may thus allow millions,or even more, of simultaneous measurements to be made.

In one aspect, the disclosure provides analytical devices containing oneor more optical resonators, e.g., lasers, that are integrated directlyinto a waveguide disposed within the substrate of the device. Nanowellscontaining samples of interest may be disposed on the surface of thesubstrate, i.e., in a layer of the device above the layer of the devicein which the waveguide is disposed, such that evanescent illuminationemanating from the waveguide is optically coupled to the nanowells, thusexciting the sample. An optical resonator of the integrated illuminationelement may be positioned so that the evanescent illumination emanatingfrom the resonator is coupled to one or more nanowells in a regiondirectly adjacent to the resonator (see, e.g., FIGS. 15A and 15B), orthe optical resonator may be positioned so that the evanescentillumination is coupled to one or more nanowells in a region remote fromthe resonator (see, e.g., FIG. 15D). In some embodiments, the opticalresonator may be positioned so that evanescent illumination is coupledto one or more nanowells that are directly adjacent to and one or morenanowells that are remote from the resonator (see, e.g., FIG. 15C). Insome embodiments, the optical resonator provides illumination to asingle nanowell (see, e.g., FIG. 15B), whereas in other embodiments, theoptical resonator provides illumination to multiple nanowells (see,e.g., FIGS. 15A, 15C, and 15D).

The optical resonator in this embodiment of an integrated illuminationelement is preferably fabricated directly into the waveguide within thesubstrate as the device itself is fabricated. The resonator, or cavity,contains a laser medium (also known as a gain medium) and two flankingmirrors disposed within the waveguide. The laser medium may be chosenfrom any suitable material, as would be understood by those skilled inthe art. For example, crystal materials, typically doped with rare-earthions (e.g. neodymium, ytterbium, or erbium) or transition metal ions(titanium or chromium) may be used (e.g., yttrium aluminium garnet(YAG), yttrium orthovanadate (YVO4), or sapphire (Al₂O₃) lasers).Alternatively, glasses (e.g. silicate or phosphate glasses, doped withlaser-active ions), semiconductors (e.g. gallium arsenide (GaAs), indiumgallium arsenide (InGaAs), or gallium nitride (GaN)), or even liquids orgases may prove suitable as a laser medium in these devices.

The mirrors of the optical resonator, which may also be referred toherein as reflectors, may also be chosen from any suitable material, asis well-known in the art. The choice of mirror will depend on theparticular device configuration. For example, where the opticalresonator is coupled to nanowells located in regions adjacent to theresonator, as, for example, those shown in FIGS. 15A and 15B, both ofthe laser mirrors, typically dielectric mirrors, may be highlyreflective mirrors, such as, for example, distributed Bragg reflectors.Such optimized mirrors may have very high reflectivity, in some caseseven higher than 99.9999%. For purposes of the instant disclosure, suchmirrors may be termed in some situations “100% mirrors” or “100%reflection mirrors”, although it should be understood that theirreflectivity is not absolute, and indeed, mirrors with less than 100%reflectivity may be suitable for use in the instant optical resonators,depending on the specific requirements.

In some embodiments, the optical resonator will amplify light along thewaveguide (see, e.g., FIGS. 15C and 15E) or will insert light into thewaveguide such that the nanowells are optically coupled to theintegrated illumination element by evanescent illumination emanatingfrom the waveguide in a region remote from the location of the opticalresonator (see, e.g., FIG. 15D). It will be understood that the mirrorsused in such devices should be chosen according to the propertiesdesired. For example, in embodiments where the optical resonator is usedto insert light into the waveguide, for example as shown in FIGS. 15D,15F, and 15G, one mirror will typically be chosen to be a high reflector(HF) mirror, whereas the other mirror will typically be chosen to be apartial reflector mirror, or output coupler (OC), because it allows somelight to leave the laser cavity and enter the waveguide. Mirrors used inoptical resonators suitable for amplifying light as it passes along thewaveguide, for example, as shown in FIGS. 15C and 15E, are chosen toallow input coupling as well as output coupling. In some embodiments,doped fiber amplifiers may be used to amplify the optical signal alongthe waveguide. In-line fiber amplifiers are well known in the art oftelecommunications.

It should be understood that further variations in the embodiments shownin FIGS. 15A-15G may be constructed without deviating from the scope ofthis aspect of the invention. For example, combinations of opticalamplifiers and non-amplifiers within a waveguide may be usefullyemployed in the devices, as may be combinations of optical resonatorsthat couple to one or more nanowells directly adjacent to the resonatorand one or more nanowells that are remote from the resonator, as wouldbe understood by the skilled artisan.

The gain medium within the optical resonator requires pumping in orderto generate light. In some embodiments, the pump may be provided by anoptical pump, for example through an opening along one side of theresonator cavity, as shown in FIG. 15F (large arrow). The optical pumpmay be, for example, flood illumination of an appropriate wavelength. Inother embodiments, the pump may be provided electrically, as illustratedin the device of FIG. 15G. The choice of pump will depend on thesituation, as would be understood by those of ordinary skill in the art.

In another aspect, the disclosure provides analytical devices thatinclude an integrated illumination element disposed on the surface ofthe substrate. In other words, the nanowells and the integratedillumination element are disposed in the same layer of the device. Inthese devices, the integrated illumination element is partly surroundedby an opaque layer or layers, to control and direct transmission ofexcitation energy into the sample. Non-limiting examples of such devicesare illustrated in FIGS. 16A-16G, 17A-17C, 18, 19, and 20. In each ofthese examples, a DNA polymerase-template complex is shown immobilizedto the bottom of a nanowell. The integrated illumination element, whichis represented by a large square on the left side of each nanowell,provides excitation energy to the nanowell, either directly from a sideof the nanowell or indirectly through a waveguide from the bottom of thenanowell. The excitation energy, which is represented by a thick arrow,is directed into the nanowell through an opening in the opaque layer.The opaque layer, represented by a thick line that partly surrounds theintegrated illumination element, may optionally form the sides of thenanowell. Emission energy from labeled nucleotides associated with theDNA polymerase-template complex is transmitted through the transparentsubstrate below the nanowell, as indicated by the thin arrows. Adetector element (not shown) is optically coupled to the nanowell, so asto capture the light emitted from the sample.

It should be understood in the context of this aspect of the inventionthat the surface of the substrate may in some cases be defined relativeto the surface where the reaction complex of interest is immobilized,i.e., the bottom of the nanowell.

Accordingly, the integrated illumination element is disposed “in” thesubstrate in the devices illustrated in FIGS. 15A-15G, whereas theintegrated illumination element is disposed “on” the surface of thesubstrate in the devices illustrated in FIGS. 16A-16G, 17A-17C, 18, 19,and 20.

In some embodiments, the device comprises an illumination element layer,an integrated illumination element, a plurality of illumination volumes,and a plurality of detector elements, wherein the integratedillumination element is disposed in the illumination element layer.

In specific embodiments, the integrated illumination element comprisesan optical resonator within a waveguide, the optical resonator comprisesa laser medium and a first and a second mirror disposed within thewaveguide, and the plurality of illumination volumes are contained in aplurality of nanowells disposed in a layer above the illuminationelement layer, wherein at least a first nanowell is optically coupled tothe waveguide and to one of the detector elements.

In other specific embodiments, the plurality of illumination volumes arecontained in a plurality of nanowells disposed in the illuminationelement layer, the plurality of detector elements are disposed in alayer below the illumination element layer, and the integratedillumination element is partly surrounded by an opaque layer, wherein atleast a first nanowell is optically coupled to the integratedillumination element and to one of the detector elements.

The placement of the opaque layer or layers around the integratedillumination element controls and directs excitation light to thenanowell. For example, the configuration shown in FIG. 16A allowsillumination to enter the nanowell from the lower portion of thenanowell. In some situations, however, it may be advantageous to placethe opaque layer only above and below the integrated illuminationelement, and allow the entire side wall of the nanowell to transmitexcitation light, as shown in FIG. 16B. In some embodiments, at least10%, at least 30%, at least 50%, at least 70%, or even at least 90% ofthe side wall of the nanowell is covered by the opaque layer. In someembodiments, at least 95%, at least 98%, at least 99%, or even more ofthe side wall of the nanowell is covered by the opaque layer.

In some embodiments, the devices may further include a transferwaveguide, as shown in FIGS. 16C and 16D. The opaque layer in theseembodiments completely covers the side wall of the nanowell but allowsexcitation light to be coupled through an opening in the opaque layerbelow the integrated illumination element. The waveguide may, in someembodiments, provide energy to the sample directly by coupling lightfrom the waveguide into the nanowell as shown in FIG. 16C, or thewaveguide may provide energy to the sample indirectly, for example byevanescent illumination, as shown in FIG. 16D. The waveguide may, insome embodiments, provide excitation energy to a single nanowell or rowof nanowells, or may provide energy to a plurality of nanowellsorganized in another pattern.

As described above, the dimensions and shape of the nanowell will dependon the desired properties and the nanowell and the methods used tofabricate the device. The depth of the nanowell (i.e., the verticaldimension of the nanowells shown in FIGS. 16A-16G) is typically from 50nm to 600 nm, but it may in some embodiments be from 100 nm to 500 nm oreven from 150 nm to 300 nm. The width of the nanowell (i.e., thehorizontal dimension of the nanowells shown in FIGS. 16A-16G) istypically from 50 to 600 nm, but it may in some embodiments be from 100to 300 nm. The shape of the nanowell (as viewed from the top of thedrawings in FIGS. 16A-16G) may be circular, elliptical, square,rectangular, or any other suitable shape. In some cases, the walls ofthe nanowell may be vertical, as shown for the nanowells of FIGS.16A-16G, whereas in some cases, the walls of the nanowell may be slopedinward or outward. For example, the nanowells could be cylindrical,cone-shaped, or inverted cone-shaped if so desired.

FIG. 16E represents an extension of the structure shown in FIG. 16A toillustrate how an array of nanowells could extend along one dimension,for example along the horizontal axis of the drawing. While not shown inthe drawing it is understood that the arrays of nanowells can alsoextend in the direction extending into and out of the plane of thedrawing, producing a two dimensional array of nanowells when viewed fromabove. For example, there can be rows of nanowells extending into andout of the plane of the drawing, each row adjacent to a waveguide, suchthat one waveguide illuminates all of the nanowells in a row. Thedrawing further illustrates that arrays of nanowells may be constructedusing repetitive features, such as the opaque layers surrounding theillumination element. By repeating such structures along one dimension,it is possible to illuminate large number of nanowells in thatdimension. In some embodiments, the repeating pattern would illuminateat least 100, at least 1000, at least 10,000, or even more nanowells.The repeating pattern could extend at least 10 μm, at least 100 μm, atleast 1 mm, at least 10 mm, or even longer in that dimension.

When the nanowell is illuminated from the side, for example as shown inthe nanowells exemplified in FIGS. 16A, 16B, 16E, 16F, and 16G, theopposite wall of the nanowell may be opaque, as shown, although undersome circumstances it may be desirable for performance or processingreasons for the opposite side wall not to be coated, allowing for anexcitation signal to pass through the opposite wall of the nanowell.

FIG. 16F illustrates another variation of the nanowell shown in FIG.16A. In this nanowell, the opaque layer on the surface of thetransparent substrate extends below the nanowell, resulting in anemission opening that is smaller than the cross-sectional dimensions ofthe nanowell itself. An exemplary device corresponding to the device ofFIG. 16F is provided in Example 1. The emission opening with dimensionssmaller than that of the nanowell can be used to limit the backgroundsignal from the nanowell. For example, when using this device foranalysis such as single molecule sequencing, it is typically desired toobserve fluorescent signal from species near the bottom of the nanowell(signal), but not to observe fluorescent signal from fluorescent speciesrandomly diffusing through the nanowell (noise). Excitation light fromthe waveguide will extend into the nanowell and may interact withfluorophores diffusing through this volume. An emission opening that issmaller than the cross sectional dimensions of the nanowell allows forlight emitted from fluorophores at the base of the well (e.g. labelednucleotides in the active site of an immobilized polymerase) to passinto the layer below, but the emission opening will limit the amount oflight emitted from diffusing fluorophores to pass into the layer below.This can result in an improved level of signal to noise (S/N) for thedevice. In some cases the emission opening has a cross sectionaldimension of from about 40 nm to about 200 nm. In some cases, theemission opening has a cross sectional dimension from about 80 nm toabout 150 nm. In some cases, the emissive opening is circular orsubstantially circular, but it can be elliptical, square, rectangular,or other shape. Where the emissive opening is circular, the crosssectional dimension is the diameter of the opening. The emission openinghas a cross-sectional area that is smaller than the area of the base ofthe nanowell. The cross-sectional area of the nanowell can be from 10%to 80% of the area of the base of the nanowell, and is typically from20% to 60% of the area of the base of the nanowell. Accordingly, in someembodiments of the device, the bottom surfaces of the plurality ofnanowells of the device are at least partially opaque.

Accordingly, an exemplary analytical device that comprises structures ofthe type displayed in FIG. 16F comprises a cylindrical nanowell that isapproximately 300 nm deep and 200 nm in diameter, and that has opaquewalls that are approximately 20 nm thick and that extend 50% to 80% downthe side wall of the nanowell. An opaque layer extends approximately 50nm into the bottom of the nanowell and leaves an approximately 100 nmdiameter emission opening to the transparent, e.g., silica, substrate.The illumination element consists of a waveguide comprising an aluminumnitride core and a silica cladding with cross-sectional dimensions ofapproximately 100 nm×200 nm. The waveguide is spaced approximately 100nm from the opaque layer on the top, bottom, and side facing thenanowells. Each waveguide illuminates a row of from 100 to 10,000nanowells, and this waveguide/nanowell pattern is repeated from 100 to10,000 times orthogonally to the row of nanowells.

In some embodiments, for example as shown in FIG. 16G, it mayadvantageous for the position and size of the opaque layer below thewaveguide to be adjusted so that the opaque layer blocks light from thewaveguide that is directed toward the detector and that would thereforeadd to the background signal, while at the same time minimizing theamount of opaque layer used, and positioning the opaque layer as faraway from the waveguide as possible, in order to limit propagationlosses through the waveguide. In some situations, however, it may bebeneficial for the portion of the opaque layer below the waveguide to berelatively close to the waveguide core. The size, composition, andposition of the portion of the opaque layer below the waveguide core maybe adjusted as desired in order to minimize the amount of backgroundexcitation signal reaching the detector and to maximize propagation oflaser signal along the waveguide. Examples of alternative materials foruse in the opaque layers, in particular opaque layers positioned betweenthe waveguide core and the detectors, are provided below. It should alsobe noted that the materials used in the various regions of an opaquelayer within a given analytical device may be the same or different,depending on the desired properties.

The opaque layers illustrated in FIGS. 16A-16G, 17A-17C, 18, 19, and 20can be from about 5 nm to about 100 nm thick, are typically 5 nm to 30nm thick but may, in some embodiments, be 5 nm to 20 nm thick. Thedistance between the illumination element and the nearest opaque layeris ideally at least 50 nm, although in some embodiments the distance maybe at least 100 nm, at least 150 nm, or at least 300 nm. It should alsobe understood that different regions of the opaque layers illustrated inFIGS. 16A-16G, 17A-17C, 18, 19, and 20 may have different thicknesses oreven been constructed of different materials, depending on the desiredproperties and behavior. Further examples of materials suitable for theconstruction of the opaque layers of the instant devices are providedbelow.

As noted above, an opaque layer may be a metallic layer, such as, forexample, a layer of aluminum, but other suitable materials may also beutilized as an opaque layer within the scope of the invention. Forexample, an optical filter layer, such as, for example, a reflectioninterference filter layer or other suitable filter layer, may serve asan opaque layer, so long as the layer is chosen and configuredappropriately according to wavelength of light being blocked.

An interference filter, as used herein, is typically a dichroic filter.The interference filter is an optical filter that reflects one or morespectral bands or lines and transmits others, while maintaining a lowcoefficient of absorption for wavelengths of interest. The interferencefilter may be high-pass, low-pass, bandpass, or band-rejection. Theinterference filter typically consists of multiple thin layers ofdielectric material having different refractive indices. There also maybe metallic layers within the interference filter.

Interference filters are wavelength-selective by virtue of theinterference effects that take place between the incident and reflectedwaves at the thin-film boundaries. An interference filter used as theopaque layer, or as part of an opaque layer, in the instant invention istypically designed to block excitation light from a waveguide. In somecases, the interference filter has many layers, e.g. from 20 to 100layers to block excitation light from the waveguide from reaching thedetectors. In some cases, for example where an opaque layer isrelatively close to the waveguide core, e.g. where the waveguide core isless than 500 nm, 300 nm, or 150 nm from the opaque layer, aninterference filter with fewer layers, e.g. less than 10 layers or with2, 3, 4, 5, 6, 7, 8, 9, or 10 layers may be used. In some cases,interference filters with 2, 4, or 6 layers is used. In some cases, aninterference filter is used as an opaque layer instead of a metalliclayer because the interference filter can block background laser lightwith lower propagation loss along the waveguide than with a metalliclayer. In some cases, an optical layer is chosen as it can provide highlevels of light blockage in a relatively thin layer.

The devices containing an integrated illumination element may optionallyinclude additional features, for example to improve the coupling ofexcitation energy to the sample. For example, as shown in FIGS. 17A and17B, one or more walls of the nanowell may be coated with a reflectivematerial and thus increase the efficiency of excitation of the sample byserving as a “micro-mirror” to reflect light back into the sample.Alternatively, or in addition, the surface of the opaque layer partlysurrounding the integrated illumination element may itself be coatedwith a reflective material to form a “micro-mirror”, as illustrated inFIG. 17C.

The efficiency of excitation coupling may optionally be furtherincreased by altering the shapes of one or more side surfaces of thenanowell, for example by fabricating the side surface of the nanowell ina concave shape, as shown in FIG. 17A, or by angling the side surface ofthe nanowell toward the bottom surface of the nanowell, as shown in FIG.17B. Alternatively, or in combination, the opaque layer partlysurrounding the integrated illumination element may be cylindrical, asshown in FIG. 17C. Use of reflective materials on other surfaces of thenanowells and altering the shape of one or more side surfaces of thenanowells in other ways to improve coupling of excitation energy to theillumination volume are considered within the scope of the disclosure.Examples of the use of micromirrors to improve the coupling efficiencyof emission energy from highly multiplexed samples to associateddetectors are provided in U.S. Patent Application Publication No.2010/0099100, which is incorporated by reference herein in its entiretyfor all purposes.

The detection of emission signals from samples in the nanowells of anyof the devices disclosed herein, including devices containing anintegrated illumination element, may be further improved by theinclusion of additional optional components to improve collection oflight by the detector elements. For example, as shown in FIG. 18, theprovision of an excitation filter between the nanowells and theassociated detector elements may improve the signal to noise ratio byblocking scattered excitation light from reaching the detectors. Thedesign of the instant devices, wherein the excitation source is disposedon the surface of the substrate is already advantageous in this regard,because the emission signal does not need to pass through the excitationbeam. In addition, the configuration of the opaque layer around theintegrated illumination element advantageously minimizes the amount ofstray excitation light able to reach the detectors and cause backgroundsignal.

FIG. 18 additionally illustrates the inclusion of a microlens opticallycoupled to each nanowell. Such microlenses focus light emitted from thenanowells and improve coupling of the emitted light to detachabledetector elements. Alternatively, the microlenses may be substitutedwith integrated detector elements, such as, for example, charge coupleddevices (CCDs), complementary metal oxide semiconductor (CMOSs), or thelike, as would be understood by those of ordinary skill in the art.

The opaque layer of the devices illustrated in FIGS. 16A-16G, 17A-17C,18, 19, and 20 may, in some embodiments, be a metallic layer. Asdescribed above, a metallic layer may cause propagation losses along awaveguide used to illuminate the samples, due to the proximity betweenthe waveguide and the metallic layer, or may otherwise decrease theoptical coupling from the waveguide to the sample. Accordingly, and asdescribed above, it may be advantageous to increase the distance betweena waveguide light source, such as may be employed in the integratedillumination element of these devices, and the opaque layer partlysurrounding it. As shown in FIG. 19, this can be accomplished byincreasing the thickness of the cladding surrounding the waveguide, inparticular, by spreading the opaque layer above and below the waveguide,and, for example, by moving the waveguide away from the nanowell. Asalso described above, however, a metallic layer in the vicinity of thenanowell may serve as a local field enhancement element to improve thecoupling of excitation light to the illuminated volume. The differenteffects should be considered and counterbalanced in the ultimate designof the integrated illumination element.

FIG. 20 illustrates two other optional components that may beincorporated into the transparent substrate of any of the instantdevices. Specifically, this figure shows a spectral diversion elementand a light redirection cone. The spectral diversion element accordingto this embodiment directs light emitted from each nanowell of thedevice to different locations according to wavelength. For example,light of spectral band 1 is directed to the left side of the deviceshown in FIG. 20, whereas light of spectral band 2 is directed to theright side of the device. As shown in the drawing, a detector, such as aCCD, a CMOS, or the like, positioned below the spectral diversionelement can thus distinguish different wavelengths of emitted lightaccording to position. Alternatively, a lens placed in this position candirect light to a detachable detector below the substrate. Intermediatecones or lenses to direct emitted light from the nanowells according tothis embodiment may also facilitate further spectral separation.

The optional spectral diversion element of the instant devices, asillustrated graphically in FIG. 20, may be, for example, the spectraldiversion element disclosed in U.S. Patent Application Publication No.2012/0021525. Such an element serves to direct light emitted from thenanowell of the device to different spatial locations on a detectorelement, depending on the wavelength of the emitted light. In otherwords, the device creates a unique pattern on the detector that dependson wavelength. In some embodiments, the spectral diversion element maybe a distinct layer within the emission zone, as illustrated in theembodiment shown in FIG. 20. In other embodiments, the spectraldiversion element may be provided by a dispersive material that fillssome or all of the space between the nanowell and the detector element.The spectral diversion element may in some embodiments be a prism,grating, or the like. It should be understood that spectral diversionelements capable of separating 2 colors, 3 colors, 4 colors, or evenmore colors are considered within the scope of the instant disclosure.

The optional light redirection cone of the instant devices, asillustrated graphically in FIG. 20, may include, or itself be a part of,additional optional features for improving the coupling of emitted lightfrom the nanowell to the detector element. Such improved detectionfeatures are disclosed in detail, for example, in U.S. PatentApplication Publication No. 2012/0021525. As described above, the use ofmicromirrors to improve the coupling efficiency of emission energy fromhighly multiplexed samples to associated detectors is disclosed in U.S.Patent Application Publication No. 2010/0099100.

It should be understood that the devices containing an integratedillumination element according to this aspect of the instant disclosuremay additionally be combined with any of the local enhancement elementsalready described above.

The integrated illumination element of the devices illustrated in FIGS.16A-16G, 17A-17C, 18, 19, and 20 may be any suitable light source. Forexample, the light source may be a waveguide configured so that itextends orthogonal to the plane of the drawings. The waveguide wouldtherefore illuminate an entire row of nanowells along that dimension. Insome embodiments, a single waveguide would illuminate at least 100, atleast 1000, at least 10,000, or even more nanowells. The waveguide couldextend at least 10 μm, at least 100 μm, at least 1 mm, at least 10 mm,or even longer. It should also be understood that the waveguide could beilluminated either by an external source, such as, for example, anexternal laser or other appropriate excitation device, or it could beilluminated by building laser elements, or other illumination elements,into the waveguide itself, as shown above and in FIGS. 15A-15G.

Alternatively, or in addition, to using a waveguide as the illuminationelement in the devices illustrated in FIGS. 16A-16G, 17A-17C, 18, 19,and 20, the light source may be a discrete light source, such as, forexample, a semiconductor laser diode, a light-emitting diode, or asolid-state laser. Non-photonic sources of excitation energy, such as,for example, plasmonic excitation, may also be considered a discretelight source in these devices. The use of plasmonic excitation toilluminate samples in highly multiplexed analytical devices is describedin U.S. Patent Application Publication No. 2012/0014837.

As just mentioned, among the discrete light sources usefully integratedinto the instant analytical devices are semiconductor laser diodes.Semiconductor lasers are diodes that are typically electrically pumped.Most commonly, a semiconductor laser diode is formed from a p-n junctionthat is electrically pumped. The recombination of electrons and holescreated by the applied current introduces optical gain. Reflection fromthe ends of the crystal results in an optical resonator. In someexamples, the resonator may be external to the semiconductor.

Laser diodes are available with a wide variety of emission wavelengths,making them well suited to providing optical excitation in, for example,fluorescent DNA sequencing reactions. Laser diodes are likewiseavailable having a wide variety of power outputs.

Vertical cavity surface-emitting lasers (VCSELs) are another type ofsemiconductor laser that may, in some embodiments, be integrated intothe analytical devices of the instant disclosure as a discrete lightsource. In a VCSEL, the emission direction is perpendicular to thesurface of the wafer. VCSEL devices typically have a more circularoutput beam than conventional laser diodes, and may, in some cases, becheaper to manufacture.

Alternatively, instead of a diode material with a bandgap, a nonlinearoptical material such as a second harmonic generation material could beused, so that when light of an appropriate angle shines on the medium,second harmonic generation creates light at a wavelength of half theilluminating wavelength. As described above, the use of a frequencyconversion system, whether in a waveguide or as part of an integratedillumination system, has the advantage of being as monochromatic as thepump light and thus relatively easy to block from generating backgroundsignal in the detection zone.

As described above, a discrete light source, such as, for example, alight emitting diode (LED), a laser diode, a nonlinear optical element,or the like, may be added to each optical confinement independently toprovide excitation light. Integration of the illumination device witheach illuminated volume on a sample chip would simplify the system inseveral ways, for example with respect to energy input, since it wouldonly be necessary to apply a DC voltage to the illumination element, andwith respect to optical output, since no data collection electronics,high speed circuitry, filters, or complex CMOS pixel structures withmultiple transistors would necessarily be needed. The followingdescription relates to a 1-color illumination device, but the sameprinciples apply equally to 1, 2, 3, 4, or more color illuminationdevices. The provision of additional colors would just entailduplicating the diodes. For example, a 4-color LED would be fabricatedby integrating 4 different diodes together.

Turning to FIGS. 21A-21B, 22, 23A-23B, and 24-29, various additionalalternative approaches to integrating a discrete light source into ananalytical device are provided. In FIGS. 21A-21B, for example, an LED,or other such light source, is placed on the surface of a substrate,directly below a nanowell, for example within an opaque, metallic layer.Where the LED and substrate are transparent to emitted light, thecollection system, including a camera or integrated detector, may beplaced below the light source, as shown in FIG. 21A. Alternatively, forexample if the substrate and LED are not transparent, the collectionsystem may be configured to collect emission light through the fluidabove the chip, for example through a cover slip as shown in FIG. 21B.The latter configuration would allow for the use of silicon-basedsubstrates, and may therefore offer more fabrication pathways and lowercost.

There are also at least two broad categories of LED structures thatcould be used as discrete light sources in such systems: opaque andtransparent. Opaque LED structures, just as with opaque substratestructures, allow the full range of device structures and fabricationtechniques, but when used with a transparent substrate, they arepreferably arranged so as not to interfere with the collection, asillustrated schematically in FIG. 22. Transparent LED structures may bearranged “in series” with the collection path, as illustratedschematically in FIGS. 23A-23B, and collection can accordingly beperformed either above or below the chip, as desired. Suchconfigurations may potentially be more efficient in terms of getting thegenerated light to the illumination volume, but the choice of materials,device structures, and processes may be somewhat more limited.

It should also be understood that the emission of light from an LED maybe highly directional. Specifically, light is typically emitted nearlyperpendicularly from the surface of the p-type layer of an LED, in acone shape. Fabrication of LEDs within the devices of the instantdisclosure should therefore take this directionality into account, suchthat the light from the LED is appropriately targeted to theillumination volume, as desired. For example, the device shown in FIG.22 would be fabricated such that light is emitted from the interiorsidewall of the illustrated LED cylinder. Other similar deviceembodiments utilizing one or more LEDs to illuminate a non-cylindricalnanowell from the side could be readily envisioned by one of ordinaryskill in the art. For example, a multi-sided nanowell could beilluminated by one or more LEDs built into one or more sidewalls of thenanowell.

There are several general approaches for patterning LEDs, as would beunderstood in the art, thus providing a great deal of flexibility indesign. For example, a simple pillbox shape could be used to illuminateeach nanowell, or simpler strip structures could be used to light uprows of nanowells. The latter could be easier to fabricate but may beless efficient in terms of electrical power required, thermaldissipation, and susceptibility to failure (e.g., a single failure couldwipe out a larger number of nanowells).

When a discrete light source is used to illuminate a nanowell, the depthof the nanowell, i.e., the vertical dimension of FIGS. 21A-21B and23A-23B, and of the side view in FIG. 22, is ideally from 50 nm to 1000nm, and the cross-sectional shape of the nanowell can be cylindrical,elliptical, square, rectangular, or any other suitable shape. Thecross-sectional dimension of the nanowell in these embodiments istypically from 50 nm to 1000 nm, but may more specifically be from 100nm to 400 nm.

In some embodiments of devices comprising a discrete light source, itmay be possible to eliminate the need for nanowells on the surface ofthe device altogether. Although the devices illustrated in FIGS.21A-21B, 22, and 23A-23B include a nanowell for sample containment, thisfunction may not be necessary in devices incorporating LEDs or otherintegrated illumination. The devices could therefore potentially befabricated without the metallic layer or the nanowells disposed in thislayer. Specifically, the small size of the LED structure itself, and thehigh directionality of the emitted light, may provide lateralconfinement in the sample plane, and such structures could be fabricatedmuch smaller than the optical resolution limit. For example, circularemitting regions, such as the one illustrated schematically in FIG. 24,or strips or other complicated shapes, such as those illustratedschematically in FIG. 25, could be utilized in the design of anintegrated illumination element. Of importance in designing thesestructures is to provide a small enough space for the lateral lightconfinement and then to balance the vertical confinement against thebackground noise introduced by excitation light that may be emitted upinto the solution, for example, in the case of traditional DNAsequencing reactions, beyond the immobilized polymerase enzyme, forexample, as shown in FIG. 26. With the integrated illumination schemes,autofluorescence accumulation does not contribute to the backgroundsignal, but noise from background diffusion should be minimized throughdesign and layout as the devices are scaled up and multiplexed.Furthermore, where the device is used in the monitoring of anenzyme-catalyzed reaction, such as in DNA sequencing reactions, thesurface of the LED is preferably fabricated to facilitate the anchoringof an enzyme, e.g., DNA polymerase, either directly to the LED emittingsurface or to an additional layer designed into the structure.

For analytical devices using integrated LEDs, the flexibility in designof LED structure allows for a large variety of different approaches. Forexample, an LED in pillbox shape may be simple and straightforward,particularly where the devices lack nanowells for sample containment,although, as described above, background diffusion noise may beproblematic in such devices. For devices that lack nanowells, thediscrete light source may be designed with this in mind to minimizesignal from background diffusion. For example, a discrete light source,such as a vertical cavity surface emitting laser (VCSEL), may beusefully employed to minimize the background signal. As illustratedschematically in FIG. 27, the laser resonator in a VCSEL device is atype of laser diode consisting of two distributed Bragg reflectormirrors parallel to the surface of the substrate. As shown in thisfigure, the upper region contains a p-type material, and the lowerregion contains an n-type material, together forming a diode junction.Such a structure generates laser beam emission from the top surface. Asillustrated schematically in FIG. 28, the laser emission from a VCSELdevice extends significantly away from the surface of the device (toppanel), and it is therefore useful to fabricate nanowells on the surfaceof the VCSEL device by adding a metallic layer over the integrateddevice and patterning the nanowells, where, for example, a DNApolymerase molecule may be immobilized (bottom panel). The inclusion ofthe nanowell structure helps to minimize background diffusion noise.VCSELs are also ideally suited to highly multiplexed analytical devices,such as the devices of the instant disclosure, due to the orientation oftheir light emission and the ability to fabricate them intwo-dimensional arrays.

In some embodiments, where the analytical devices display simplifiedstructures lacking a metallic layer or nanowells, it may be advantageousto fabricate a modified structure that does not emit light at all. Forexample, if the mirror and cavity are re-tuned to the structure shown inthe top panel of FIG. 29, for example, where the, e.g., 99% laserreflector is replaced by a 100% laser reflector, and the laser resonatorbecomes a cavity resonator (i.e., a vertical cavity resonator (VCR)),there is no laser light emission from the surface and thus no backgrounddiffusion noise. In such a device, the vertical light confinementfunction of the nanowell/ZMW is replaced by the evanescent field at thetop surface of the resonator, which extends from the surface only 10-20nm, and the lateral confinement function of the nanowell/ZMW is replacedby the small VCSEL geometry. In all cases, the geometries are balancedagainst the fluorophore concentration for the ultimate necessary signalto noise ratio. Depending on the substrate, collection of emissionsignal may be either below the device (for a transparent substrate) orabove the device through the fluid sample (for an opaque substrate).

As described above, whether using an extended illumination element, suchas a laser or waveguide illumination element, or using a discrete lightsource, such as an LED or other similarly configured light source, it isenvisioned that the arrays of the instant analytical devices can extendin each direction by at least 100, at least 1000, at least 10,000, oreven more nanowells. Depending on the exact layout of the devices,specifically on whether the nanowells are organized in regular rows orin some other pattern on the device, and whether the devices are shapedas squares, rectangles, or some other geometric shape, the devices areexpected to comprise at least 1,000, at least 10,000, at least 100,000,at least 1,000,000, or even at least 10,000,000 illumination volumeswithin those nanowells.

In yet another aspect, the disclosure provides analytical devices of thefollowing numbered paragraphs.

1. An analytical device comprising:

an optical waveguide comprising an optical core and a cladding;

a metallic layer disposed on a surface of the cladding;

a plurality of nanometer-scale apertures disposed in the metallic layerin sufficient proximity to the optical waveguide to be illuminated by anevanescent field emanating from the waveguide when optical energy ispassed through the optical core; and

a plurality of local field enhancement elements associated with theplurality of apertures.

2. The analytical device of paragraph 1, wherein the local fieldenhancement elements comprise a high dielectric material or metal in thevicinity of the apertures.

3. The analytical device of paragraph 2, wherein the high dielectricmaterial or metal is arranged in a geometric pattern around theapertures.

4. The analytical device of paragraph 3, wherein the geometric patternis selected from the group consisting of a circle, a series ofconcentric circles, a C aperture, a triangle pair, and a diamond.

5. The analytical device of paragraph 2, wherein the high dielectricmaterial or metal is Al₂O₃, copper, silver, gold, or aluminum.

6. The analytical device of paragraph 5, wherein the high dielectricmaterial or metal is Al₂O₃.

7. The analytical device of paragraph 5, wherein the high dielectricmaterial or metal is copper.

8. The analytical device of paragraph 1, wherein the apertures arerecessed into the cladding.

9. The analytical device of paragraph 1, wherein the thickness of thecladding between the optical core and the metallic layer decreases inthe vicinity of the apertures.

10. The analytical device of paragraph 9, wherein the thickness of thecladding is from 150 to 300 nm.

11. The analytical device of paragraph 10, wherein the thickness of thecladding is about 200 nm.

12. The analytical device of paragraph 1, wherein the local fieldenhancement elements comprise the shape of the nanometer-scaleapertures.

13. The analytical device of paragraph 12, wherein the shape of thenanometer-scale apertures is selected from the group consisting of a Caperture, a triangle pair, and a diamond.

14. An analytical device comprising:

an optical waveguide comprising an optical core and a cladding;

a metallic layer disposed on the surface of the cladding; and

a plurality of nanometer-scale apertures disposed in the metallic layerin sufficient proximity to the optical waveguide to be illuminated by anevanescent field emanating from the waveguide when optical energy ispassed through the optical core;

wherein the optical core has a thickness, a width, and a cross-sectionalarea, and wherein the cross-sectional area is decreased at locationswhere the evanescent field illuminates the apertures.

15. The analytical device of paragraph 14, wherein the cross-sectionalarea is decreased by adiabatic tapers.

16. The analytical device of paragraph 14, wherein the thickness of theoptical core is maintained, and the cross-sectional area is decreased bydecreasing the width of the optical core.

17. The analytical device of paragraph 16, wherein the optical energy istransverse electric polarized light.

18. The analytical device of paragraph 14, wherein the width of theoptical core is maintained, and the cross-sectional area is decreased bydecreasing the thickness of the optical core.

19. The analytical device of paragraph 18, wherein the optical energy istransverse magnetic polarized light.

20. The analytical device of paragraph 14, further comprising aplurality of local field enhancement elements associated with theplurality of apertures.

21. The analytical device of paragraph 20, wherein the local fieldenhancement elements comprise a high dielectric material or metal in thevicinity of the apertures.

22. The analytical device of paragraph 21, wherein the high dielectricmaterial or metal is arranged in a geometric pattern around theaperture.

23. The analytical device of paragraph 22, wherein the geometric patternis selected from the group consisting of a circle, a series ofconcentric circles, a C aperture, a triangle pair, and a diamond.

24. The analytical device of paragraph 21, wherein the high dielectricmaterial or metal is Al₂O₃, copper, silver, gold, or aluminum.

25. The analytical device of paragraph 24, wherein the high dielectricmaterial or metal is Al₂O₃.

26. The analytical device of paragraph 24, wherein the high dielectricmaterial or metal is copper.

27. The analytical device of paragraph 20, wherein the apertures arerecessed into the cladding.

28. The analytical device of paragraph 20, wherein the thickness of thecladding between the optical core and the metallic layer decreases inthe vicinity of the apertures.

29. The analytical device of paragraph 28, wherein the thickness of thecladding is from 150 to 300 nm.

30. The analytical device of paragraph 29, wherein the thickness of thecladding is about 200 nm.

31. The analytical device of paragraph 20, wherein the local fieldenhancement elements comprise the shape of the nanometer-scaleapertures.

32. The analytical device of paragraph 31, wherein the shape of thenanometer-scale apertures is selected from the group consisting of a Caperture, a triangle pair, and a diamond.

33. An analytical device comprising:

-   -   an optical waveguide comprising a plurality of optical cores and        a cladding;    -   a plurality of nanometer-scale apertures disposed on a surface        of the device in sufficient proximity to the optical waveguide        to be illuminated by an evanescent field emanating from the        waveguide when optical energy is passed through the plurality of        optical cores; and    -   a plurality of detectors optically coupled to the plurality of        nanometer-scale apertures;    -   wherein the optical cores are not in direct alignment between        the nanometer-scale apertures and their optically coupled        detectors.

34. The analytical device of paragraph 33, wherein the plurality ofnanometer-scale apertures are illuminated by an evanescent fieldemanating from at least two optical cores.

35. The analytical device of paragraph 33, further comprising an opaquelayer disposed between the optical waveguide and the plurality ofoptical detectors, wherein the opaque layer comprises a plurality ofopenings in direct alignment with the nanometer-scale apertures andtheir optically coupled detectors.

36. The analytical device of paragraph 33, wherein the device furthercomprises a plurality of local field enhancement elements associatedwith the plurality of apertures.

37. The analytical device of paragraph 36, wherein the local fieldenhancement element comprises a high dielectric material or metal in thevicinity of the aperture.

38. The analytical device element of paragraph 37, wherein the highdielectric material or metal is arranged in a geometric pattern aroundthe aperture.

39. The analytical device element of paragraph 38, wherein the geometricpattern is selected from the group consisting of a circle, a series ofconcentric circles, a C aperture, a triangle pair, and a diamond.

40. The analytical device of paragraph 37, wherein the high dielectricmaterial or metal is Al₂O₃, copper, silver, gold, or aluminum.

41. The analytical device element of paragraph 40, wherein the highdielectric material or metal is Al₂O₃.

42. The analytical device element of paragraph 40, wherein the highdielectric material or metal is copper.

43. The analytical device element of paragraph 33, wherein the aperturesare recessed into the cladding.

44. The analytical device of paragraph 33, wherein the thickness of thecladding decreases in the vicinity of the apertures.

45. The analytical device of paragraph 44, wherein the thickness of thecladding thickness is from 150 to 300 nm.

46. The analytical device of paragraph 45, wherein the thickness of thecladding is about 200 nm.

47. An analytical device comprising:

an optical waveguide comprising an optical core and a cladding; and

a plurality of nanometer-scale apertures disposed on a surface of thedevice in sufficient proximity to the optical waveguide to beilluminated by an evanescent field emanating from the waveguide whenoptical energy of a defined wavelength is passed through the opticalcore;

wherein the wavelength of the optical energy is modulated as it passesthrough the optical core.

48. The analytical device of paragraph 47, wherein the optical waveguidecomprises a non-linear optical material.

49. The analytical device of paragraph 48, wherein the non-linearoptical material is placed periodically within the optical core.

50. The analytical device of paragraph 48, wherein the non-linearoptical material is placed within the cladding.

51. The analytical device of paragraph 47, wherein the wavelengthconversion is effected through phase matching.

52. The analytical device of paragraph 47, wherein the wavelengthconversion is effected through electro-optical effects.

53. The analytical device of paragraph 47, wherein the optical energy ismodulated by second harmonic generation.

54. The analytical device of paragraph 47, wherein the optical energy ismodulated by third harmonic generation.

55. The analytical device of paragraph 47, wherein the optical energy ismodulated by optical parametric amplification.

56. The analytical device of paragraph 47, further comprising aplurality of local field enhancement elements associated with theplurality of apertures.

57. The analytical device of paragraph 56, wherein the local fieldenhancement elements comprise a high dielectric material or metal in thevicinity of the aperture.

58. The analytical device of paragraph 57, wherein the high dielectricmaterial or metal is arranged in a geometric pattern around theaperture.

59. The analytical device of paragraph 58, wherein the geometric patternis selected from the group consisting of a circle, a series ofconcentric circles, a C aperture, a triangle pair, and a diamond.

60. The analytical device of paragraph 57, wherein the high dielectricmaterial or metal is Al₂O₃, copper, silver, gold, or aluminum.

61. The analytical device of paragraph 60, wherein the high dielectricmaterial or metal is Al₂O₃.

62. The analytical device of paragraph 60, wherein the high dielectricmaterial or metal is copper.

63. The analytical device of paragraph 56, wherein the apertures arerecessed into the cladding.

64. The analytical device of paragraph 56, wherein the thickness of thecladding decreases in the vicinity of the apertures.

65. The analytical device of paragraph 64, wherein the thickness of thecladding is from 150 to 300 nm.

66. The analytical device of paragraph 65, wherein the thickness of thecladding is about 200 nm.

67. The analytical device of paragraph 56, wherein the local fieldenhancement elements comprise the shape of the nanometer-scaleapertures.

68. The analytical device of paragraph 67, wherein the shape of thenanometer-scale apertures is selected from the group consisting of a Caperture, a triangle pair, and a diamond.

69. The analytical device of any one of paragraphs 1-68, wherein theanalytical device further comprises a plurality of analytes disposed inanalyte regions within the plurality of nanometer-scale apertures.

70. The analytical device of paragraph 69, wherein the plurality ofanalytes comprise a plurality of biological samples.

71. The analytical device of paragraph 70, wherein the plurality ofbiological samples comprise a plurality of nucleic acids.

72. The analytical device of any one of paragraphs 1-68, wherein theanalytical device comprises at least 1,000, at least 10,000, at least100,000, at least 1,000,000, or at least 10,000,000 nanometer-scaleapertures.

It will be readily apparent to one of ordinary skill in the relevantarts that other suitable modifications and adaptations to the analyticaldevices described herein may be made without departing from the scope ofthe invention or any embodiment thereof. Having now described thepresent invention in detail, the same will be more clearly understood byreference to the following Example, which is included herewith forpurposes of illustration only and is not intended to be limiting of theinvention.

EXAMPLE Example 1: Analytical Device with Side Waveguide Illumination ofNanoscale Apertures

FIG. 30 shows a cross-sectional view of a portion of an analyticaldevice of the invention for side waveguide illumination of nanoscaleapertures/nanowells. The cross-section shows a nanowell 3066 illuminatedby waveguide core 3065. The analytical device has one million nanowellsin an array of 1000 by 1000. The waveguide core 3065 extends into andout of the plane of the drawing, illuminating 1000 nanowells. There are1000 waveguides, aligned parallel to one another, each illuminating arow of 1000 nanowells.

The device is produced using semiconductor processing technology on aCMOS wafer 3010. The CMOS wafer in this example is a detector having twomillion pixels. In FIG. 30, two pixels are represented in cross-sectionas 3012 and 3014. Each nanowell within this exemplary device isoptically associated with two pixels.

A filter layer 3020 is positioned on top of the CMOS wafer. The filterlayer is produced such that a specific filter is associated with thepixel directly below it. For each set of two pixels associated with aparticular nanowell, there are two different filters, e.g. 3022 and3024, each allowing a different set of wavelengths of light to pass tothe pixel below. The filter layer is approximately 1 micron thick.

A lens layer 3030 is positioned on top of the filter layer. In thedevice of FIG. 30, this lens layer is a Fresnel lens layer comprising abottom oxide layer 3032 and a top layer 3034 comprising, for example,alpha-silicon. The lens layer directs light emitted from the nanowell3066 through the filter layer and onto the pixels 3012 and 3014. Thethickness of the lens layer is approximately 5 microns. The thickness ofthe bottom oxide layer is selected to allow for the light redirected bythe lens elements to be effectively separated and directed to theappropriate pixel.

A laser interference rejection filter 3040 is positioned on top of thelens layer. This laser rejection filter specifically reflects laserlight from the waveguide while allowing signal light of longerwavelength emitted from the nanowell to pass. In the exemplary device,an antireflective coating 3042, about 80 nm thick, is positioned on thetop surface of the laser interference rejection filter. Theantireflective coating is designed to transmit the wavelengths of signallight. The exemplary device additionally includes an optional lighttransmission layer 3050 comprising silicon dioxide on the top surface ofthe laser interference rejection filter. This transparent layer acts asa spacer for controlling the manner in which light emitted from thenanowell enters the layers below. The transparent layer is about 2microns thick.

A waveguide/nanowell layer, or illumination element layer, 3060 ispositioned on the top surface of the transparent layer. Thewaveguide/nanowell layer includes a waveguide core 3065 which isdisposed to the side of nanowell 3066. The waveguide is composed of arelatively high refractive index material such as silicon nitride. Thewaveguide is approximately 150 nm thick and 400 nm wide. The edge of thewaveguide core 3065 is approximately 500 nm from the nanowell 3066. Inthe exemplary device, the waveguide is surrounded by silicon dioxidehaving a thickness of approximately 300 nm. The lower part of thewaveguide/nanowell layer includes an opaque layer 3062 composed ofaluminum that is 10 nm to 20 nm thick. In the device of FIG. 30, theopaque layer 3062 is a continuous layer except for an emission opening3067, which is positioned under the nanowell 3066. The emission openingis round with a diameter of about 100 nm. The nanowell itself iscylindrical with a diameter of about 300 nm. An opaque aluminum layer3064 is positioned on the top surface of the waveguide/nanowell layer.The opaque aluminum layer is approximately 20 nm to 30 nm thick. Thislayer typically covers the entire top surface of the device, except forthe nanowell. It protects the solution above the device from exposure toexcitation light from the waveguide.

In the exemplary device, the overall thickness of the portion of thedevice above CMOS layer 3010 is approximately 9 microns.

For performing single-molecule sequencing using the exemplary analyticaldevice, a single polymerase-template complex is immobilized within theemission opening 3067 at the bottom of nanowell 3066. The top of thedevice is exposed to the reagents required for carrying out nucleic acidsynthesis including phospho-labeled nucleic acids. Laser excitationlight is passed through waveguide 3065 as the polymerase-dependentnucleic acid synthesis occurs at the polymerase-template complex.Excitation light from the evanescent field emanating from the waveguideis coupled into the nanowell 3066, exciting fluorophores within thenanowell. Nucleotides which are incorporated can be distinguished fromfreely diffusing nucleotides, as incorporated nucleotides have a longerresidence time. In addition, the emission opening 3067 preferentiallyallows the passage of light from species near the bottom and center ofthe nanowell, such as those associated with the polymerase enzyme.

Emitted light from the labels is directed to the filters by the lenslayer toward the two pixels below the nanowell. The four nucleotides aredifferently labeled, for example with two different colors, each at twodifferent amplitudes. Thus, one pixel, e.g. 3012 will detect the eventscorresponding to two of the nucleotides, and the identity of each can bedistinguished by differences in amplitude. The other pixel will detectevents corresponding to the other two nucleotides. By monitoring theincorporation events for the four nucleotides over time, the sequence ofthe template nucleic acid can be determined. The signals from the CMOSdetector are sent to a computer system for analyzing the data includingmaking the best base calls based on the information available.

All patents, patent publications, and other published referencesmentioned herein are hereby incorporated by reference in theirentireties as if each had been individually and specificallyincorporated by reference herein.

While specific examples have been provided, the above description isillustrative and not restrictive. Any one or more of the features of thepreviously described embodiments can be combined in any manner with oneor more features of any other embodiments in the present invention.Furthermore, many variations of the invention will become apparent tothose skilled in the art upon review of the specification. The scope ofthe invention should, therefore, be determined by reference to theappended claims, along with their full scope of equivalents.

What is claimed is:
 1. An analytical device comprising: a substrate; anintegrated illumination element disposed on the substrate; a pluralityof illumination volumes disposed above the integrated illuminationelement; and a plurality of detector elements disposed below theintegrated illumination element; wherein the integrated illuminationelement comprises a plurality of discrete light sources, and wherein theplurality of discrete light sources are each disposed directly below anillumination volume, and the plurality of discrete light sourcesdirectly illuminate the plurality of illumination volumes from below. 2.The analytical device of claim 1, wherein light emitted from an analytedisposed within at least a first illumination volume is opticallycoupled to at least a first detector element through at least a firstdiscrete light source.
 3. The analytical device of claim 1, wherein thediscrete light sources are semiconductor laser diodes, light-emittingdiodes, solid-state lasers, or vertical cavity surface-emitting lasers.4. The analytical device of claim 1, wherein the discrete light sourcesare diode light sources.
 5. The analytical device of claim 4, whereinthe diode light sources comprise an electrically pumped p-n junction. 6.The analytical device of claim 1, wherein the illumination volumes areilluminated by light emitted nearly perpendicularly from a top surfaceof the discrete light sources.
 7. The analytical device of claim 6,wherein the light is emitted in a cone shape from the top surface of thediscrete light sources.
 8. The analytical device of claim 1, wherein theillumination volumes are illuminated by an evanescent field emanatingfrom a top surface of the discrete light sources.
 9. The analyticaldevice of claim 1, wherein the discrete light sources are arranged in astrip structure.
 10. The analytical device of claim 1, wherein at leasta first detector element is disposed directly below a first illuminationvolume and a first discrete light source.
 11. The analytical device ofclaim 1, further comprising an opaque layer disposed on the integratedillumination element.
 12. The analytical device of claim 1, wherein theplurality of illumination volumes are contained in a plurality ofnanowells disposed on the substrate, wherein at least a first nanowellis optically coupled to a first discrete light source and to a firstdetector element.
 13. The analytical device of claim 12, furthercomprising an opaque layer disposed on the integrated illuminationelement, wherein the plurality of nanowells are disposed in the opaquelayer, and wherein the first nanowell is optically coupled to the firstdiscrete light source and to the first detector element through a bottomsurface of the first nanowell.
 14. The analytical device of claim 12,further comprising a conductor element and an insulator elementassociated with the first discrete light source, wherein the insulatorelement is disposed between the conductor element and the opaque layer.15. The analytical device of claim 1, further comprising an analytedisposed within at least one illumination volume.
 16. The analyticaldevice of claim 15, wherein the analyte comprises a biological sample.17. The analytical device of claim 16, wherein the biological samplecomprises a nucleic acid.
 18. The analytical device of claim 16, whereinthe biological sample comprises a polymerase enzyme.
 19. The analyticaldevice of claim 1, wherein the analytical device comprises at least1,000 illumination volumes.